forked from Minki/linux
4106f83a9f
Swappiness isn't a safe sysctl. Setting it to 0 for example can hang a system. That's a corner case but even setting it to 10 or lower can waste enormous amounts of cpu without making much progress. We've customers who wants to use swappiness but they can't because of the current implementation (if you change it so the system stops swapping it really stops swapping and nothing works sane anymore if you really had to swap something to make progress). This patch from Kurt Garloff makes swappiness safer to use (no more huge cpu usage or hangs with low swappiness values). I think the prev_priority can also be nuked since it wastes 4 bytes per zone (that would be an incremental patch but I wait the nr_scan_[in]active to be nuked first for similar reasons). Clearly somebody at some point noticed how broken that thing was and they had to add min(priority, prev_priority) to give it some reliability, but they didn't go the last mile to nuke prev_priority too. Calculating distress only in function of not-racy priority is correct and sure more than enough without having to add randomness into the equation. Patch is tested on older kernels but it compiles and it's quite simple so... Overall I'm not very satisified by the swappiness tweak, since it doesn't rally do anything with the dirty pagecache that may be inactive. We need another kind of tweak that controls the inactive scan and tunes the can_writepage feature (not yet in mainline despite having submitted it a few times), not only the active one. That new tweak will tell the kernel how hard to scan the inactive list for pure clean pagecache (something the mainline kernel isn't capable of yet). We already have that feature working in all our enterprise kernels with the default reasonable tune, or they can't even run a readonly backup with tar without triggering huge write I/O. I think it should be available also in mainline later. Cc: Nick Piggin <npiggin@suse.de> Signed-off-by: Kurt Garloff <garloff@suse.de> Signed-off-by: Andrea Arcangeli <andrea@suse.de> Signed-off-by: Fengguang Wu <wfg@mail.ustc.edu.cn> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> |
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| .. | ||
| allocpercpu.c | ||
| backing-dev.c | ||
| bootmem.c | ||
| bounce.c | ||
| fadvise.c | ||
| filemap_xip.c | ||
| filemap.c | ||
| fremap.c | ||
| highmem.c | ||
| hugetlb.c | ||
| internal.h | ||
| Kconfig | ||
| madvise.c | ||
| Makefile | ||
| memory_hotplug.c | ||
| memory.c | ||
| mempolicy.c | ||
| mempool.c | ||
| migrate.c | ||
| mincore.c | ||
| mlock.c | ||
| mmap.c | ||
| mmzone.c | ||
| mprotect.c | ||
| mremap.c | ||
| msync.c | ||
| nommu.c | ||
| oom_kill.c | ||
| page_alloc.c | ||
| page_io.c | ||
| page-writeback.c | ||
| pdflush.c | ||
| prio_tree.c | ||
| quicklist.c | ||
| readahead.c | ||
| rmap.c | ||
| shmem_acl.c | ||
| shmem.c | ||
| slab.c | ||
| slob.c | ||
| slub.c | ||
| sparse-vmemmap.c | ||
| sparse.c | ||
| swap_state.c | ||
| swap.c | ||
| swapfile.c | ||
| thrash.c | ||
| tiny-shmem.c | ||
| truncate.c | ||
| util.c | ||
| vmalloc.c | ||
| vmscan.c | ||
| vmstat.c | ||