Messages in this thread |  | | Date | Sat, 22 Mar 2008 19:09:14 -0300 | From | "Carlos R. Mafra" <> | Subject | 103 sec. latency: sync_page() with TASK_UNINTERRUPTIBLE (?) |
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Today I've repeated the experience described in http://lkml.org/lkml/2008/3/15/111 and I got these latencytop numbers(!)
Cause Maximum Percentage sync_page __lock_page handle_mm_fault do_page_faul103659.0 msec 59.8 % get_request_wait __make_request generic_make_reque1992.0 msec 10.2 % get_request_wait __make_request generic_make_reque1620.7 msec 4.6 % sync_page __lock_page find_lock_page filemap_fault399.3 msec 3.4 % sync_buffer __wait_on_buffer __bread ext3_get_bran292.9 msec 1.3 % sync_page __lock_page handle_mm_fault do_page_faul200.5 msec 0.3 % Scheduler: waiting for cpu 155.9 msec 18.9 % sync_page __lock_page handle_mm_fault do_page_faul117.5 msec 0.1 % congestion_wait try_to_free_pages __alloc_pages re103.5 msec 0.2 % r_code
Process X (2910) sync_page __lock_page handle_mm_fault do_page_faul103659.0 msec 98.5 % Scheduler: waiting for cpu 64.6 msec 1.3 % sync_page __lock_page find_lock_page filemap_fault 51.4 msec 0.2 %lt do_page_fault error_code sync_buffer __wait_on_buffer __bread ext3_get_bran 17.8 msec 0.0 % ext3_get_block do_mpage_readpage mpage_readpa sync_page __lock_page handle_mm_fault do_page_faul 9.1 msec 0.0 %ig ault
The experience goes like this:
1) Boot with 2.6.25-rc6-00243-g028011e 2) Log into X 3) Open a 380MB file with xjed
It takes more than 6 minutes to load the file, and meanwhile I experience very bad desktop interactivity (like 1 minute to the result of pressing F12 in Window Maker to appear in the screen).
If, after step 2), I start using firefox, thunderbird, play some music etc and then close all these apps and go to step 3), the loading finishes in about 2 minutes (and I have very good interactivity meanwhile).
So I noticed that when xjed is opening the file it is in 'D' state (reported by ps), and while greping the kernel source code for 'sync_page' I've found this comment in mm/filemap.c:
/** * __lock_page - get a lock on the page, assuming we need to sleep to get it * @page: the page to lock * * Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary. If some * random driver's requestfn sets TASK_RUNNING, we could busywait. However * chances are that on the second loop, the block layer's plug list is empty, * so sync_page() will then return in state TASK_UNINTERRUPTIBLE. */
"Ugly. Running sync_page() in state TASK_UNINTERRUPTIBLE is scary."
It appears that my problem with xjed in 'D' state while loading, and sync_page() appearing in latencytop with 103 secs of latency may be related through the "ugliness" described above.
So I was wondering if there is a way to fix this. Note that this issue does not happen if I load the file after using the computer for a while, so it is not impossible to have good interactivity while loading that big file.
I am sorry that I am scattering reports about this issue all over the place.
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