Very slow to open when in a folder with many images

[starkgate]

 * Xviewer version: 2.6.2
 * Distribution: Mint Xfce 20

Issue
Xviewer takes minutes to open a 1 megapixel image in a folder with many other images (12k in my case). In the same situation, Pix opens instantly.
Xviewer also freezes Thunar until it finally opens. Very frustrating.

Steps to reproduce

1. Many images in a folder
2. Open one of the images with Xviewer

Expected behaviour
Should open immediately and work asynchronously from Thunar.

[rob-vh]

same observation, xviewer 3.0.2 on linux mint 20.2.
strikingly, using the forward button WITHIN xviewer is almost instantaneous.

[ygerlach]

The problem is, that xviewer opens all images in the folder.

xviewer is called with something like this:

xviewer imagea.jpg imageb.jpg imagec.jpg ..... [all other 10k images]

I guess loading the opened image, display it and then loading the other images in the background would be the better way to do this.

Maybe not load all images but just the next 10 or something like this.

But i see why this is done. When you have a folder with images and you select only a part of the images and open that, you expect only the selected images to be opened. That is why xviewer is started with a list of files. But still a annoying bug.

[dpantel]

Is this being worked on at all?

[privat3dancer]

I can confirm this bug exists in xviewer 3.2.10 . Cannot open any images in a directory with ~100k png files when called from bash (e.g. xviewer image.png). No window appears. Console says:

malloc(): invalid size (unsorted) Aborted (core dumped)

Slightly better behavior than pix, which will open the image and then subsequently lock up cinnamon (probably hitting multiple bugs there). I assume these are related to unwanted "features" triggered by loading a single file, e.g. preparing to slideshow other files in the directory regardless of user intent by loading a totally unpredictable chunk of filesystem into an array.

But i see why this is done. When you have a folder with images and you select only a part of the images and open that, you expect only the selected images to be opened. That is why xviewer is started with a list of files. But still a annoying bug.

I did not follow this comment or its logic at all. Opening a file should open a single file and not interact with any other files.

[ygerlach]

I can confirm this bug exists in xviewer 3.2.10 . Cannot open any images in a directory with ~100k png files when called from bash (e.g. xviewer image.png). No window appears. Console says:

malloc(): invalid size (unsorted) Aborted (core dumped)

Im not sure this is the same bug. In the cases i observed, xviewer was called with many images as arguments and did not crash, but took very long (>1min) to load. Especially on slower storage. Does this also happen, if you copy one image out of the folder and open it somewhere, where its less crowded? Also try the --disable-gallery option.

As far as i looked into the code it seems to query the content type of each file (g_file_info_get_content_type). I don't know the concrete implementation, but i believe this might open the file to check for some magic numbers. If this is the case, in a directory with many pictures, on a slow storage, this will create a lot of slow random reads.

The bad thing is, that if you have enough RAM, Linux will at some point start to cache the file and the latency might disappear. This makes it harder to investigate this problem. Having the media on a external storage device and unplugging it between tests may help. Also filling up the RAM with junk and disabling swap may also help. Maybe there are some kernel parameters to disable this kind of caching? Anyway, this is something to keep in mind while testing.

Maybe the best way to implement a fix would be to not process every image at the beginning, but only the 10 next and the 10 previous. This may have the side effect that xviewer shows "Image 1/2000" at the beginning, but after scanning some files, reduces that number, as some of the files may be corrupt, empty or no image at all. A option would be to hide the number until all images where scanned. But even if the number might not be totally correct, i would prefer that over xviewer taking > 1min to open.

But i see why this is done. When you have a folder with images and you select only a part of the images and open that, you expect only the selected images to be opened. That is why xviewer is started with a list of files. But still a annoying bug.

I did not follow this comment or its logic at all. Opening a file should open a single file and not interact with any other files.

I think removing the list of files from xviewer and letting nemo only open one image is not the correct solution as it removes or breaks these features and user experiences:

• having a folder sorted by a specific attribute, even if you open only one image users expect the next image to be the same as in nemo. even if the user only clicked on one image.
• Having a specific selection inside a folder opening a subset of available files

[privat3dancer]

You're right. It is a different bug. I submitted #201.

is not the correct solution as it removes or breaks these features and user experiences

Don't do anything without any indication of user intent. This is linux. Either that or don't make this the default image viewer in the distribution. As a default viewer, it should load an image in any directory immediately without doing anything else.

[ygerlach]

Don't do anything without any indication of user intent. This is linux. Either that or don't make this the default image viewer in the distribution. As a default viewer, it should load an image in any directory immediately without doing anything else.

I disagree. An image viewer may allow a user to view neighbouring pictures (and may fetch them to generate a thumbnail), even if they where not directly opened.
But i agree, loading the clicked image should be the highest priority to any image viewer. Crashing while loading any image (with or without user intention) is not acceptable.

[privat3dancer]

What do you expect the application cat to do when you call cat filename.txt ?

[ygerlach]

If i disable the Map plugin from the xviewer-plugins package the loading time for a folder with 7.5k jpg images is reduced from ~580s to ~5s.

This is the log with the map plugin and job logging enabled:

$ XVIEWER_DEBUG_JOBS=1 xviewer /[path to folder with 7.5k jpg]/

[0,000101 (0,000101)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) No jobs in queue
[0,000122 (0,000021)] ../src/xviewer-job-scheduler.c:102 (xviewer_job_scheduler_dequeue_job) Wating for jobs ...
[0,851012 (0,850890)] ../src/xviewer-jobs.c:771 (xviewer_job_model_new) XviewerJobModel (0x5625f1c80590) job was CREATED
[0,851027 (0,000015)] ../src/xviewer-job-scheduler.c:57 (xviewer_job_scheduler_enqueue_job) ENQUEUED XviewerJobModel (0x5625f1c80590) with priority 2
[0,851046 (0,000019)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) DEQUEUED XviewerJobModel (0x5625f1c80590)
[0,851060 (0,000014)] ../src/xviewer-job-scheduler.c:147 (xviewer_job_process) PROCESSING a XviewerJobModel (0x5625f1c80590)
[5,293605 (4,442545)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) No jobs in queue
[5,293620 (0,000015)] ../src/xviewer-job-scheduler.c:102 (xviewer_job_scheduler_dequeue_job) Wating for jobs ...
[5,293629 (0,000009)] ../src/xviewer-jobs.c:152 (notify_finished) XviewerJobModel (0x5625f1c80590) job was FINISHED
[5,298305 (0,004676)] ../src/xviewer-jobs.c:602 (xviewer_job_load_new) XviewerJobLoad (0x5625f1d70050) job was CREATED
[5,298318 (0,000013)] ../src/xviewer-job-scheduler.c:57 (xviewer_job_scheduler_enqueue_job) ENQUEUED XviewerJobLoad (0x5625f1d70050) with priority 2
[5,298333 (0,000015)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) DEQUEUED XviewerJobLoad (0x5625f1d70050)
[5,298341 (0,000008)] ../src/xviewer-job-scheduler.c:147 (xviewer_job_process) PROCESSING a XviewerJobLoad (0x5625f1d70050)
[5,299127 (0,000786)] ../src/xviewer-jobs.c:117 (notify_progress) XviewerJobLoad (0x5625f1d70050) job update its progress to -> 0,01
[5,401150 (0,102023)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) No jobs in queue
[5,401165 (0,000015)] ../src/xviewer-job-scheduler.c:102 (xviewer_job_scheduler_dequeue_job) Wating for jobs ...
[581,552978 (576,151813)] ../src/xviewer-jobs.c:117 (notify_progress) XviewerJobLoad (0x5625f1d70050) job update its progress to -> 1,00

[snipped 130 duplicates]

[581,553697 (0,000006)] ../src/xviewer-jobs.c:152 (notify_finished) XviewerJobLoad (0x5625f1d70050) job was FINISHED

[581,680786 (0,127089)] ../src/xviewer-jobs.c:1297 (xviewer_job_thumbnail_new) XviewerJobThumbnail (0x5625f1545c50) job was CREATED

[581,680910 (0,000124)] ../src/xviewer-job-scheduler.c:57 (xviewer_job_scheduler_enqueue_job) ENQUEUED XviewerJobThumbnail (0x5625f1545c50) with priority 2

[581,680922 (0,000012)] ../src/xviewer-jobs.c:1297 (xviewer_job_thumbnail_new) XviewerJobThumbnail (0x5625f1545ca0) job was CREATED

[581,680928 (0,000006)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) DEQUEUED XviewerJobThumbnail (0x5625f1545c50)

[581,680938 (0,000010)] ../src/xviewer-job-scheduler.c:147 (xviewer_job_process) PROCESSING a XviewerJobThumbnail (0x5625f1545c50)

[581,681011 (0,000073)] ../src/xviewer-job-scheduler.c:57 (xviewer_job_scheduler_enqueue_job) ENQUEUED XviewerJobThumbnail (0x5625f1545ca0) with priority 2

[581,681018 (0,000007)] ../src/xviewer-jobs.c:1297 (xviewer_job_thumbnail_new) XviewerJobThumbnail (0x5625f1545cf0) job was CREATED

[581,681121 (0,000103)] ../src/xviewer-job-scheduler.c:57 (xviewer_job_scheduler_enqueue_job) ENQUEUED XviewerJobThumbnail (0x5625f1545cf0) with priority 2

[581,681128 (0,000007)] ../src/xviewer-jobs.c:1297 (xviewer_job_thumbnail_new) XviewerJobThumbnail (0x5625f1545d40) job was CREATED

[581,681217 (0,000089)] ../src/xviewer-job-scheduler.c:57 (xviewer_job_scheduler_enqueue_job) ENQUEUED XviewerJobThumbnail (0x5625f1545d40) with priority 2

[581,681785 (0,000568)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) DEQUEUED XviewerJobThumbnail (0x5625f1545ca0)

[581,681791 (0,000006)] ../src/xviewer-job-scheduler.c:147 (xviewer_job_process) PROCESSING a XviewerJobThumbnail (0x5625f1545ca0)

[581,682725 (0,000934)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) DEQUEUED XviewerJobThumbnail (0x5625f1545cf0)

[581,682735 (0,000010)] ../src/xviewer-job-scheduler.c:147 (xviewer_job_process) PROCESSING a XviewerJobThumbnail (0x5625f1545cf0)

[581,683736 (0,001001)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) DEQUEUED XviewerJobThumbnail (0x5625f1545d40)

[581,683745 (0,000009)] ../src/xviewer-job-scheduler.c:147 (xviewer_job_process) PROCESSING a XviewerJobThumbnail (0x5625f1545d40)

[581,684773 (0,001028)] ../src/xviewer-job-scheduler.c:95 (xviewer_job_scheduler_dequeue_job) No jobs in queue

[581,684781 (0,000008)] ../src/xviewer-job-scheduler.c:102 (xviewer_job_scheduler_dequeue_job) Wating for jobs ...

[581,896653 (0,211872)] ../src/xviewer-jobs.c:152 (notify_finished) XviewerJobThumbnail (0x5625f1545c50) job was FINISHED

[581,897420 (0,000767)] ../src/xviewer-jobs.c:152 (notify_finished) XviewerJobThumbnail (0x5625f1545ca0) job was FINISHED

[581,897522 (0,000102)] ../src/xviewer-jobs.c:152 (notify_finished) XviewerJobThumbnail (0x5625f1545cf0) job was FINISHED

[581,897618 (0,000096)] ../src/xviewer-jobs.c:152 (notify_finished) XviewerJobThumbnail (0x5625f1545d40) job was FINISHED

Cpu usage during the hang is quite low (<3%) but disk reads are at a few MB/s (probably the most my drive has available)

After this i closed and reopend xviewer with the same arguments. It now opend in about 7s. I cleared my cache by allocating a very big chunk of random data in memory. Then i run xviewer again. It again took very long to load. But this time i attached with gdb and got a hold of this stacktrace, mentioning libmap.so (the map xviewer plugin).

(gdb) bt full

#0  __GI___libc_read (nbytes=65535, buf=0x560d52f1b010, fd=27) at ../sysdeps/unix/sysv/linux/read.c:26
        sc_ret = 65535
        sc_cancel_oldtype = 0
        sc_ret = <optimized out>
#1  __GI___libc_read (fd=27, buf=buf@entry=0x560d52f1b010, nbytes=nbytes@entry=65535) at ../sysdeps/unix/sysv/linux/read.c:24
#2  0x00007f0ef3e0d471 in read (__nbytes=65535, __buf=0x560d52f1b010, __fd=<optimized out>, __fd=<optimized out>, __buf=<optimized out>, __nbytes=<optimized out>) at /usr/include/x86_64-linux-gnu/bits/unistd.h:38
        file = 0x560d52631cf0
        res = -1
#3  g_local_file_input_stream_read (stream=<optimized out>, buffer=0x560d52f1b010, count=65535, cancellable=0x0, error=0x0) at ../../../gio/glocalfileinputstream.c:153
        file = 0x560d52631cf0
        res = -1
#4  0x00007f0ef3d511f7 in g_input_stream_read (stream=0x560d52631cf0, buffer=buffer@entry=0x560d52f1b010, count=count@entry=65535, cancellable=cancellable@entry=0x0, error=error@entry=0x0) at ../../../gio/ginputstream.c:198
        class = 0x560d523d9130
        res = <optimized out>
        __func__ = "g_input_stream_read"
#5  0x00007f0ef3f1d075 in xviewer_image_real_load (error=0x0, job=<optimized out>, data2read=<optimized out>, img=<optimized out>) at ../src/xviewer-image.c:1126
        mime_type = <optimized out>
        buffer = 0x560d52f1b010 "\377\330\377", <incomplete sequence \340>
        set_metadata = 1
        input_stream = 0x560d52631cf0
        failed = 0
        md_reader = 0x0
        bytes_read = <optimized out>
        use_rsvg = <optimized out>
        read_image_data = <optimized out>
        priv = <optimized out>
        format = <optimized out>
        loader = <optimized out>
        bytes_read_total = <optimized out>
        first_run = 1
        read_only_dimension = <optimized out>
        priv = <optimized out>
        success = 0
        __func__ = "xviewer_image_load"
#6  xviewer_image_load (img=<optimized out>, data2read=<optimized out>, job=<optimized out>, error=0x0) at ../src/xviewer-image.c:1437
        priv = <optimized out>
        success = 0
        __func__ = "xviewer_image_load"
#7  0x00007f0eecdc2589 in  () at /usr/lib/xviewer/plugins/libmap.so
#8  0x00007f0ef355feba in  () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#9  0x00007f0ef35614de in gtk_tree_model_foreach () at /lib/x86_64-linux-gnu/libgtk-3.so.0
#10 0x00007f0eecdc28a6 in  () at /usr/lib/xviewer/plugins/libmap.so
#14 0x00007f0ef3ca5863 in <emit signal ??? on instance ???> (instance=instance@entry=0x560d52490170, signal_id=<optimized out>, detail=detail@entry=0) at ../../../gobject/gsignal.c:3587
        var_args = {{gp_offset = 24, fp_offset = 48, overflow_arg_area = 0x7ffd7474e1a0, reg_save_area = 0x7ffd7474e0e0}}
    #11 0x00007f0ef3c87d2f in g_closure_invoke (closure=0x560d52ec9da0, return_value=0x0, n_param_values=1, param_values=0x7ffd7474df10, invocation_hint=0x7ffd7474de90) at ../../../gobject/gclosure.c:830
                marshal = 0x7f0ef3c8a120 <g_cclosure_marshal_VOID__VOID>
                marshal_data = 0x0
                in_marshal = 0
                real_closure = 0x560d52ec9d80
                __func__ = "g_closure_invoke"
    #12 0x00007f0ef3ca3c36 in signal_emit_unlocked_R (node=node@entry=0x560d526acd70, detail=detail@entry=0, instance=instance@entry=0x560d52490170, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffd7474df10) at ../../../gobject/gsignal.c:3777
                tmp = <optimized out>
                handler = 0x560d52ec4b80
                accumulator = 0x0
                emission = {next = 0x7ffd7474e350, instance = 0x560d52490170, ihint = {signal_id = 221, detail = 0, run_type = (G_SIGNAL_RUN_FIRST | G_SIGNAL_ACCUMULATOR_FIRST_RUN)}, state = EMISSION_RUN, chain_type = 0x4}
                class_closure = 0x560d526acd40
                hlist = <optimized out>
                handler_list = 0x560d52ec4b80
                return_accu = 0x0
                accu = {g_type = 0x0, data = {{v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer = 0x0}}}
                signal_id = 221
                max_sequential_handler_number = 10021
                return_value_altered = 0
    #13 0x00007f0ef3ca5614 in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffd7474e0c0) at ../../../gobject/gsignal.c:3530
                instance_and_params = 0x7ffd7474df10
                signal_return_type = <optimized out>
                param_values = 0x7ffd7474df28
                node = <optimized out>
                i = <optimized out>
                n_params = <optimized out>
                __func__ = "g_signal_emit_valist"
#15 0x00007f0ef3f41f4f in xviewer_window_obtain_desired_size (image=<optimized out>, width=<optimized out>, height=<optimized out>, window=0x560d52490170) at ../src/xviewer-window.c:1337
        screen = <optimized out>
        monitor = {x = 0, y = 360, width = 1920, height = 1080}
        allocation = {x = 0, y = 0, width = 540, height = 450}
        final_width = 460
        final_height = 918
        screen_width = 1920
        screen_height = 1080
        window_width = 540
        window_height = <optimized out>
        img_width = <optimized out>
        img_height = <optimized out>
        view_width = <optimized out>
        deco_width = <optimized out>
        deco_height = <optimized out>
        __func__ = "xviewer_window_obtain_desired_size"
#19 0x00007f0ef3ca5863 in <emit signal ??? on instance ???> (instance=<optimized out>, signal_id=<optimized out>, detail=detail@entry=0) at ../../../gobject/gsignal.c:3587
        var_args = {{gp_offset = 40, fp_offset = 48, overflow_arg_area = 0x7ffd7474e6a0, reg_save_area = 0x7ffd7474e5e0}}
    #16 0x00007f0ef3c87d2f in g_closure_invoke (closure=0x560d5244fbc0, return_value=0x0, n_param_values=3, param_values=0x7ffd7474e3e0, invocation_hint=0x7ffd7474e360) at ../../../gobject/gclosure.c:830
                marshal = 0x7f0ef3f13530 <xviewer_marshal_VOID__INT_INT>
                marshal_data = 0x0
                in_marshal = 0
                real_closure = 0x560d5244fba0
                __func__ = "g_closure_invoke"
    #17 0x00007f0ef3ca3c36 in signal_emit_unlocked_R (node=node@entry=0x7f0ed012e0d0, detail=detail@entry=0, instance=instance@entry=0x7f0ed02eaca0, emission_return=emission_return@entry=0x0, instance_and_params=instance_and_params@entry=0x7ffd7474e3e0) at ../../../gobject/gsignal.c:3777
                tmp = <optimized out>
                handler = 0x560d5315cc40
                accumulator = 0x0
                emission = {next = 0x0, instance = 0x7f0ed02eaca0, ihint = {signal_id = 407, detail = 0, run_type = (G_SIGNAL_RUN_FIRST | G_SIGNAL_ACCUMULATOR_FIRST_RUN)}, state = EMISSION_RUN, chain_type = 0x4}
                class_closure = 0x7f0ed012e0a0
                hlist = <optimized out>
                handler_list = 0x560d5315cc40
                return_accu = 0x0
                accu = {g_type = 0x0, data = {{v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer = 0x0}, {v_int = 0, v_uint = 0, v_long = 0, v_ulong = 0, v_int64 = 0, v_uint64 = 0, v_float = 0, v_double = 0, v_pointer = 0x0}}}
                signal_id = 407
                max_sequential_handler_number = 10001
                return_value_altered = 0
    #18 0x00007f0ef3ca5614 in g_signal_emit_valist (instance=<optimized out>, signal_id=<optimized out>, detail=<optimized out>, var_args=var_args@entry=0x7ffd7474e5c0) at ../../../gobject/gsignal.c:3530
                instance_and_params = 0x7ffd7474e3e0
                signal_return_type = <optimized out>
                param_values = 0x7ffd7474e3f8
                node = <optimized out>
                i = <optimized out>
                n_params = <optimized out>
                __func__ = "g_signal_emit_valist"
#20 0x00007f0ef3f143e2 in do_emit_size_prepared_signal (img=<optimized out>) at ../src/xviewer-image.c:438
#21 0x00007f0ef3b8ec44 in g_main_dispatch (context=0x560d52320560) at ../../../glib/gmain.c:3419
        dispatch = 0x7f0ef3b8aed0 <g_idle_dispatch>
        prev_source = 0x0
        begin_time_nsec = 0
        was_in_call = 0
        user_data = 0x7f0ed02eaca0
        callback = 0x7f0ef3f143c0 <do_emit_size_prepared_signal>
        cb_funcs = <optimized out>
        cb_data = <optimized out>
        need_destroy = <optimized out>
        source = 0x7f0ed012afe0
        current = 0x560d52346ab0
        i = 0
#22 g_main_context_dispatch (context=0x560d52320560) at ../../../glib/gmain.c:4137
#23 0x00007f0ef3be42b8 in g_main_context_iterate.constprop.0 (context=context@entry=0x560d52320560, block=block@entry=1, dispatch=dispatch@entry=1, self=<optimized out>) at ../../../glib/gmain.c:4213
        max_priority = 2147483647
        timeout = 11857
        some_ready = 1
        nfds = <optimized out>
        allocated_nfds = <optimized out>
        fds = 0x560d52345840
#24 0x00007f0ef3b8c3e3 in g_main_context_iteration (context=context@entry=0x560d52320560, may_block=may_block@entry=1) at ../../../glib/gmain.c:4278
        retval = <optimized out>
#25 0x00007f0ef3db3fb5 in g_application_run (application=0x560d52318120, argc=argc@entry=2, argv=argv@entry=0x7ffd7474e958) at ../../../gio/gapplication.c:2569
        arguments = 0x560d52345840
        status = 0
        context = 0x560d52320560
        acquired_context = <optimized out>
        __func__ = "g_application_run"
#26 0x0000560d509704bc in main (argc=<optimized out>, argv=<optimized out>) at ../src/main.c:133
        error = 0x0
        ctx = <optimized out>

unfortunately it seems there are no dbg symbols available for xviewer-plugins

[privat3dancer]

I don't have map enabled, and the load time for a file in a directory with >200k image files is ... too long for me to wait. Minutes, if not hours. A core is pinned at 100% on the process, and the perf says:

# Event count (approx.): 67463502534
#
# Children      Self  Command  Shared Object               Symbol                                      
# ........  ........  .......  ..........................  ............................................
#
    26.19%    11.75%  xviewer  libglib-2.0.so.0.7200.4     [.] g_sequence_iter_next
            |          
            |--14.44%--g_sequence_iter_next
            |          
            |--2.47%--g_hash_table_lookup
            |          
             --0.67%--g_hash_table_insert

    17.47%     8.06%  xviewer  libglib-2.0.so.0.7200.4     [.] g_hash_table_lookup
            |          
             --13.18%--g_hash_table_lookup

    16.41%    10.51%  xviewer  libglib-2.0.so.0.7200.4     [.] g_hash_table_insert
            |          
             --7.31%--g_hash_table_insert

    14.39%     9.33%  xviewer  libglib-2.0.so.0.7200.4     [.] g_sequence_iter_is_end
            |          
            |--5.06%--g_sequence_iter_is_end
            |          
            |--1.82%--g_hash_table_lookup
            |          
             --0.53%--0x79954510f7b9

     7.49%     0.00%  xviewer  libglib-2.0.so.0.7200.4     [.] 0x000079954513380c
            |
            ---0x79954513380c

     5.10%     3.96%  xviewer  libglib-2.0.so.0.7200.4     [.] g_direct_hash
            |          
            |--1.39%--g_hash_table_lookup
            |          
             --1.14%--g_direct_hash

     4.62%     4.62%  xviewer  libglib-2.0.so.0.7200.4     [.] 0x0000000000067808
            |          
             --0.55%--g_hash_table_insert

     4.12%     4.12%  xviewer  libglib-2.0.so.0.7200.4     [.] 0x000000000006780e
            |          
            |--0.59%--g_hash_table_insert
            |          
             --0.52%--0x799524251200
                       g_sequence_iter_next

     3.97%     0.00%  xviewer  libglib-2.0.so.0.7200.4     [.] 0x0000799545133824
            |
            ---0x799545133824

     3.84%     0.00%  xviewer  libglib-2.0.so.0.7200.4     [.] 0x0000799545133830

So it's probably all this hash table stuff in src/xviewer-metadata-details.c .Sorry, I didn't have the bandwidth to look more closely right now. Somewhere in there must be logic to get metadata from the entire directory, which is problematic.

[clefebvre]

I don't see why xviewer needs to do anything else than just loading the given picture.

If the gallery is enabled, it can load the number of thumbnails required to be visible.

If the user presses Next or Previous, it can read the directory when that happens.

There's no need to actually read the entire directory imo.