Messages in this thread | | | Date | Tue, 9 Nov 2004 11:36:20 -0800 | From | Andrew Morton <> | Subject | Re: balance_pgdat(): where is total_scanned ever updated? |
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Marcelo Tosatti <marcelo.tosatti@cyclades.com> wrote: > > On Sat, Nov 06, 2004 at 04:11:14PM -0800, Andrew Morton wrote: > > Chuck Ebbert <76306.1226@compuserve.com> wrote: > > > > > > Kernel version is 2.6.9, but I see no updates to this function in BK-current. > > > How is total_scanned ever updated? AFAICT it is always zero. > > > > It's a bug which was introduced months ago when we added struct > > reclaim_state. > > > > > In mm/vmscan.c:balance_pgdat(), there are these references to total_scanned > > > (missing whitepace indicated by "^"): > > > > > > > > > 977: int total_scanned, total_reclaimed; > > > > > > 983: total_scanned = 0; > > > > > > 1076: if (total_scanned > SWAP_CLUSTER_MAX * 2 && > > > 1077: total_scanned > total_reclaimed+total_reclaimed/2) > > > ^ ^ ^ ^ > > > > > > 1088: if (total_scanned && priority < DEF_PRIORITY - 2) > > > > > > > > > Could this be part of the problems with reclaim? Or have I missed something? > > > > I had a patch which fixes it in -mm for a while. It does increase the > > number of pages which are reclaimed via direct reclaim and decreases the > > number of pages which are reclaimed by kswapd. As one would expect from > > throttling kswapd. This seems undesirable. > > Hi Andrew, > > Do you have any numbers to backup the claim "It does increase the > number of pages which are reclaimed via direct reclaim and decreases the > number of pages which are reclaimed by kswapd", please?
Run a workload and watch /proc/vmstat. iirc, the one-line total_scanned fix takes the kswapd-vs-direct reclaim rate from 1:1 to 1:3 or thereabouts.
> Because linux-2.6.10-rc1-mm2 (and 2.6.9) completly ignores sc->may_writepage > under normal operation, its only used when laptop_mode is on: > > if (laptop_mode && !sc->may_writepage) > goto keep_locked; > > Is this intentional ???
yup. In laptop mode we try to scan further to find a clean page rather than spinning up the disk for a writepage.
> > I'm leaving this alone until it can be demonstrated that fixing it improves > > kernel behaviour in some manner. > > I dont see it working at all? >
There's lots of useful info in /proc/vmstat. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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