On 05/06/2014 07:39, Ian Lepore wrote: > On Tue, 2014-05-06 at 03:42 +0000, Alan Cox wrote: >> Author: alc >> Date: Tue May 6 03:42:04 2014 >> New Revision: 265418 >> URL: http://svnweb.freebsd.org/changeset/base/265418 >> >> Log: >> Prior to r254304, a separate function, vm_pageout_page_stats(), was used to >> periodically update the reference status of the active pages. This >> function >> was called, instead of vm_pageout_scan(), when memory was not scarce. The >> objective was to provide up to date reference status for active pages in >> case memory did become scarce and active pages needed to be deactivated. >> >> The active page queue scan performed by vm_pageout_page_stats() was >> virtually identical to that performed by vm_pageout_scan(), and so r254304 >> eliminated vm_pageout_page_stats(). Instead, vm_pageout_scan() is >> called with the parameter "pass" set to zero. The intention was that when >> pass is zero, vm_pageout_scan() would only scan the active queue. However, >> the variable page_shortage can still be greater than zero when memory is >> not >> scarce and vm_pageout_scan() is called with pass equal to zero. >> Consequently, the inactive queue may be scanned and dirty pages laundered >> even though that was not intended by r254304. This revision fixes that. >> >> Reported by: avg >> MFC after: 1 week >> Sponsored by: EMC / Isilon Storage Division >> >> Modified: >> head/sys/vm/vm_pageout.c >> >> Modified: head/sys/vm/vm_pageout.c >> ============================================================================== >> --- head/sys/vm/vm_pageout.c Tue May 6 03:38:04 2014 (r265417) >> +++ head/sys/vm/vm_pageout.c Tue May 6 03:42:04 2014 (r265418) >> @@ -942,13 +942,15 @@ vm_pageout_scan(struct vm_domain *vmd, i >> */ >> addl_page_shortage = 0; >> >> - deficit = atomic_readandclear_int(&vm_pageout_deficit); >> - >> /* >> * Calculate the number of pages we want to either free or move >> * to the cache. >> */ >> - page_shortage = vm_paging_target() + deficit; >> + if (pass > 0) { >> + deficit = atomic_readandclear_int(&vm_pageout_deficit); >> + page_shortage = vm_paging_target() + deficit; >> + } else >> + page_shortage = deficit = 0; >> >> /* >> * maxlaunder limits the number of dirty pages we flush per scan. >> > Does this address the observation that several folks have made on > current@ that pages are being pushed to swap much more agressively than > in the past, even when the system doesn't seem short of memory? >
I hope so. Please let me know if you see any difference. I also suspect that another side-effect of r254304 is that we are swapping out idle processes sooner, before memory has become scarce. Has anyone observed this behavior? Alan _______________________________________________ svn-src-head@freebsd.org mailing list http://lists.freebsd.org/mailman/listinfo/svn-src-head To unsubscribe, send any mail to "svn-src-head-unsubscr...@freebsd.org"
