Re: [PATCH] O11int for interactivity

William Lee Irwin III
2003-08-05T05:01:44Z

On Tue, 05 Aug 2003 13:38:34 +1000, Nick Piggin said:
>> Of course some minimum read _latency_ would be required: this
>> could actually be done easily with strace come to think of it.
>> Maybe some xmms mapped memory is being swapped out? But that
>> would be more of a VM problem.

On Tue, Aug 05, 2003 at 12:54:10AM -0400, Valdis.Kletnieks@vt.edu wrote:
> I was seeing some CPU-related pauses, but once Con's work got to O7 or so,
> those disappeared. I'm *quite* convinced that the remaining glitches
> are VM related, mostly because every glitch seems to be associated with
> an increase in the 'pswpout' field in /proc/vmstat (yes, I tested
> with stuff like "for (;;) do cat /proc/vmstat; sleep 1 done;".

Could I get logs of the stuff?

On Tue, Aug 05, 2003 at 12:54:10AM -0400, Valdis.Kletnieks@vt.edu wrote:
> The *odd* part is that the pgpgin, pgpgout, and pswpin numbers do
> *NOT* seem to be correlated. High I/O loads from read/write don't
> seem to cause a problem - untarring the Linux distro won't do it,
> running badblocks won't do it. But if somebody has to swap out, all
> hell breaks loose...

Is the swapfile/partition on the same disk as the music? Is the disk IDE?

On Tue, Aug 05, 2003 at 12:54:10AM -0400, Valdis.Kletnieks@vt.edu wrote:
> Hmm.. looking at mm/page_io.c, it seems swap_writepage() calls
> get_swap_bio with GFP_NOIO, while readdpage() uses GFP_KERNEL. I
> wonder if that GFP_NOIO is causing ugliness - that's really
> __GFP_WAIT, and the comments in bio_alloc() are pretty clear that it
> can block. And remember we're not getting into this code unless
> we're already under memory pressure....
> (And if somebody tells me how to instrument a -test2-mm4 kernel so I
> can tell if I'm on crack or not, I'll happily do so....)

Well, sleepometer is around, but probably needs merging.

-- wli