On Wed, 01 Aug 2007 03:36:30 -0400 Eric St-Laurent <[EMAIL PROTECTED]> wrote:
> On Tue, 2007-31-07 at 23:09 -0700, Andrew Morton wrote: > > > +vm-dont-run-touch_buffer-during-buffercache-lookups.patch > > > > A little VM experiment. See changelog for details. > > > We don't have any tests to determine the effects of this, and nobody will > > bother setting one up, so ho hum, this remains in -mm for ever. > > > I don't think there's any point in doing this until we have some decent > > testcases. > > > Hi Andrew, > > > For which problem this patch was coded? Good question. I think the current behaviour is just wrong. What the effect of changing it will be is hard to predict - probably little. > Is it a potential fix to the > updatedb problem? That's one workload which is particularly susceptible to the problemn which that patch addresses, yes. But in my (brief) testing it didn't make musch difference. > Is the patch effective without the filesystem dependant change you talk > about? (I use reiserfs) Yes, it'll work as designed with reiserfs. > I've been thinking about a test case for the updatedb problem: > > 1. Script or program that create a large number of directories and zero > sized files. Same setup for everyone to have reproducible results. > > 2. Run updatedb on those. > > 3. Observe the effects (with vmstat, slabinfo and meminfo) before, > during and after the updatedb run. > > 4. Do something to trigger some reclaim like copying a large file. > > 5. See the effects. > > > What do you think? What would be the ideal test case for the problem in > your opinion? Sounds good, yes. Or you could do something more real-worldly like start up OO, firefox and friends, then run /etc/cron.daily/everything and see what the before-and-after effects are. The aggregate info we're looking for is captured in /proc/meminfo: swapped, Mapped, Cached, Buffers. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
