The patch titled Subject: mm: vmscan: forcibly scan highmem if there are too many buffer_heads pinning highmem has been added to the -mm tree. Its filename is mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem.patch Before you just go and hit "reply", please: a) Consider who else should be cc'ed b) Prefer to cc a suitable mailing list as well c) Ideally: find the original patch on the mailing list and do a reply-to-all to that, adding suitable additional cc's *** Remember to use Documentation/SubmitChecklist when testing your code *** The -mm tree is included into linux-next and is updated there every 3-4 working days ------------------------------------------------------ From: Mel Gorman <mel@xxxxxxxxx> Subject: mm: vmscan: forcibly scan highmem if there are too many buffer_heads pinning highmem Stuart Foster reported on https://bugzilla.kernel.org/show_bug.cgi?id=42578 that copying large amounts of data from NTFS caused an OOM kill on 32-bit X86 with 16G of memory. Andrew Morton correctly identified that the problem was NTFS was using 512 blocks meaning each page had 8 buffer_heads in low memory pinning it. In the past, direct reclaim used to scan highmem even if the allocating process did not specify __GFP_HIGHMEM but not any more. kswapd no longer will reclaim from zones that are above the high watermark. The intention in both cases was to minimise unnecessary reclaim. The downside is on machines with large amounts of highmem that lowmem can be fully consumed by buffer_heads with nothing trying to free them. The following patch is based on a suggestion by Andrew Morton to extend the buffer_heads_over_limit case to force kswapd and direct reclaim to scan the highmem zone regardless of the allocation request or watermarks. Addresses https://bugzilla.kernel.org/show_bug.cgi?id=42578 Reported-by: Stuart Foster <smf.linux@xxxxxxxxxxxx> Tested-by: Stuart Foster <smf.linux@xxxxxxxxxxxx> Signed-off-by: Mel Gorman <mgorman@xxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Rik van Riel <riel@xxxxxxxxxx> Cc: Christoph Lameter <cl@xxxxxxxxx> Cc: stable <stable@xxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/vmscan.c | 19 +++++++++++++++++++ 1 file changed, 19 insertions(+) diff -puN mm/vmscan.c~mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem mm/vmscan.c --- a/mm/vmscan.c~mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem +++ a/mm/vmscan.c @@ -2238,6 +2238,14 @@ static bool shrink_zones(int priority, s unsigned long nr_soft_scanned; bool aborted_reclaim = false; + /* + * If the number of buffer_heads in the machine exceeds the maximum + * allowed level, force direct reclaim to scan the highmem zone as + * highmem pages could be pinning lowmem pages storing buffer_heads + */ + if (buffer_heads_over_limit) + sc->gfp_mask |= __GFP_HIGHMEM; + for_each_zone_zonelist_nodemask(zone, z, zonelist, gfp_zone(sc->gfp_mask), sc->nodemask) { if (!populated_zone(zone)) @@ -2727,6 +2735,17 @@ loop_again: */ age_active_anon(zone, &sc, priority); + /* + * If the number of buffer_heads in the machine + * exceeds the maximum allowed level and this node + * has a highmem zone, force kswapd to reclaim from + * it to relieve lowmem pressure. + */ + if (buffer_heads_over_limit && is_highmem_idx(i)) { + end_zone = i; + break; + } + if (!zone_watermark_ok_safe(zone, order, high_wmark_pages(zone), 0, 0)) { end_zone = i; _ Subject: Subject: mm: vmscan: forcibly scan highmem if there are too many buffer_heads pinning highmem Patches currently in -mm which might be from mel@xxxxxxxxx are make-swapin-readahead-skip-over-holes-fix.patch vmscan-reclaim-at-order-0-when-compaction-is-enabled.patch vmscan-kswapd-carefully-call-compaction.patch vmscan-kswapd-carefully-call-compaction-fix.patch vmscan-only-defer-compaction-for-failed-order-and-higher.patch compact_pgdat-workaround-lockdep-warning-in-kswapd.patch mm-compaction-make-compact_control-order-signed.patch mm-compaction-make-compact_control-order-signed-fix.patch mm-vmscan-forcibly-scan-highmem-if-there-are-too-many-buffer_heads-pinning-highmem.patch smp-introduce-a-generic-on_each_cpu_mask-function.patch slub-only-ipi-cpus-that-have-per-cpu-obj-to-flush.patch mm-only-ipi-cpus-to-drain-local-pages-if-they-exist.patch add-debugging-aid-for-memory-initialisation-problems.patch -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html