user/sven/linux.git/include/linux/swap.h, branch tmp/leds/core

memcg: fix shmem's swap accounting

2009-01-08T16:31:10Z

Now, you can see following even when swap accounting is enabled. 1. Create Group 01, and 02. 2. allocate a "file" on tmpfs by a task under 01. 3. swap out the "file" (by memory pressure) 4. Read "file" from a task in group 02. 5. the charge of "file" is moved to group 02. This is not ideal behavior. This is because SwapCache which was loaded by read-ahead is not taken into account.. This is a patch to fix shmem's swapcache behavior. - remove mem_cgroup_cache_charge_swapin(). - Add SwapCache handler routine to mem_cgroup_cache_charge(). By this, shmem's file cache is charged at add_to_page_cache() with GFP_NOWAIT. - pass the page of swapcache to shrink_mem_cgroup. Signed-off-by: KAMEZAWA Hiroyuki Cc: Daisuke Nishimura Cc: Balbir Singh Cc: Paul Menage Cc: Li Zefan Cc: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: swappiness

2009-01-08T16:31:08Z

Currently, /proc/sys/vm/swappiness can change swappiness ratio for global reclaim. However, memcg reclaim doesn't have tuning parameter for itself. In general, the optimal swappiness depend on workload. (e.g. hpc workload need to low swappiness than the others.) Then, per cgroup swappiness improve administrator tunability. Signed-off-by: KAMEZAWA Hiroyuki Signed-off-by: KOSAKI Motohiro Cc: Balbir Singh Cc: Daisuke Nishimura Cc: Hugh Dickins Cc: KOSAKI Motohiro Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: mem+swap controller core

2009-01-08T16:31:05Z

This patch implements per cgroup limit for usage of memory+swap. However there are SwapCache, double counting of swap-cache and swap-entry is avoided. Mem+Swap controller works as following. - memory usage is limited by memory.limit_in_bytes. - memory + swap usage is limited by memory.memsw_limit_in_bytes. This has following benefits. - A user can limit total resource usage of mem+swap. Without this, because memory resource controller doesn't take care of usage of swap, a process can exhaust all the swap (by memory leak.) We can avoid this case. And Swap is shared resource but it cannot be reclaimed (goes back to memory) until it's used. This characteristic can be trouble when the memory is divided into some parts by cpuset or memcg. Assume group A and group B. After some application executes, the system can be.. Group A -- very large free memory space but occupy 99% of swap. Group B -- under memory shortage but cannot use swap...it's nearly full. Ability to set appropriate swap limit for each group is required. Maybe someone wonder "why not swap but mem+swap ?" - The global LRU(kswapd) can swap out arbitrary pages. Swap-out means to move account from memory to swap...there is no change in usage of mem+swap. In other words, when we want to limit the usage of swap without affecting global LRU, mem+swap limit is better than just limiting swap. Accounting target information is stored in swap_cgroup which is per swap entry record. Charge is done as following. map - charge page and memsw. unmap - uncharge page/memsw if not SwapCache. swap-out (__delete_from_swap_cache) - uncharge page - record mem_cgroup information to swap_cgroup. swap-in (do_swap_page) - charged as page and memsw. record in swap_cgroup is cleared. memsw accounting is decremented. swap-free (swap_free()) - if swap entry is freed, memsw is uncharged by PAGE_SIZE. There are people work under never-swap environments and consider swap as something bad. For such people, this mem+swap controller extension is just an overhead. This overhead is avoided by config or boot option. (see Kconfig. detail is not in this patch.) TODO: - maybe more optimization can be don in swap-in path. (but not very safe.) But we just do simple accounting at this stage. [nishimura@mxp.nes.nec.co.jp: make resize limit hold mutex] [hugh@veritas.com: memswap controller core swapcache fixes] Signed-off-by: KAMEZAWA Hiroyuki Cc: Li Zefan Cc: Balbir Singh Cc: Pavel Emelyanov Signed-off-by: Daisuke Nishimura Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

memcg: handle swap caches

2009-01-08T16:31:05Z

SwapCache support for memory resource controller (memcg) Before mem+swap controller, memcg itself should handle SwapCache in proper way. This is cut-out from it. In current memcg, SwapCache is just leaked and the user can create tons of SwapCache. This is a leak of account and should be handled. SwapCache accounting is done as following. charge (anon) - charged when it's mapped. (because of readahead, charge at add_to_swap_cache() is not sane) uncharge (anon) - uncharged when it's dropped from swapcache and fully unmapped. means it's not uncharged at unmap. Note: delete from swap cache at swap-in is done after rmap information is established. charge (shmem) - charged at swap-in. this prevents charge at add_to_page_cache(). uncharge (shmem) - uncharged when it's dropped from swapcache and not on shmem's radix-tree. at migration, check against 'old page' is modified to handle shmem. Comparing to the old version discussed (and caused troubles), we have advantages of - PCG_USED bit. - simple migrating handling. So, situation is much easier than several months ago, maybe. [hugh@veritas.com: memcg: handle swap caches build fix] Reviewed-by: Daisuke Nishimura Tested-by: Daisuke Nishimura Signed-off-by: KAMEZAWA Hiroyuki Cc: Hugh Dickins Cc: Li Zefan Cc: Balbir Singh Cc: Pavel Emelyanov Signed-off-by: Hugh Dickins Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

badpage: zap print_bad_pte on swap and file

2009-01-06T23:59:07Z

Complete zap_pte_range()'s coverage of bad pagetable entries by calling print_bad_pte() on a pte_file in a linear vma and on a bad swap entry. That needs free_swap_and_cache() to tell it, which will also have shown one of those "swap_free" errors (but with much less information). Similar checks in fork's copy_one_pte()? No, that would be more noisy than helpful: we'll see them when parent and child exec or exit. Where do_nonlinear_fault() calls print_bad_pte(): omit !VM_CAN_NONLINEAR case, that could only be a bug in sys_remap_file_pages(), not a bad pte. VM_FAULT_OOM rather than VM_FAULT_SIGBUS? Well, okay, that is consistent with what happens if do_swap_page() operates a bad swap entry; but don't we have patches to be more careful about killing when VM_FAULT_OOM? Signed-off-by: Hugh Dickins Cc: Nick Piggin Cc: Christoph Lameter Cc: Mel Gorman Cc: Rik van Riel Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swapfile: swapon randomize if nonrot

2009-01-06T23:59:05Z

Swap allocation has always started from the beginning of the swap area; but if we're dealing with a solidstate swap device which can only remap blocks within limited zones, that would sooner wear out the first zone. Therefore sys_swapon() test whether blk_queue is non-rotational, and if so randomize the cluster_next starting position for allocation. If blk_queue is nonrot, note SWP_SOLIDSTATE for later use, and report it with an "SS" at the right end of the kernel's "Adding ... swap" message (so that if it's both nonrot and discardable, "SSD" will be shown there). Perhaps something should be shown in /proc/swaps (swapon -s), but we have to be more cautious before making any addition to that format. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Cc: David Woodhouse Cc: Jens Axboe Cc: Matthew Wilcox Cc: Joern Engel Cc: James Bottomley Cc: Donjun Shin Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swapfile: swap allocation use discard

2009-01-06T23:59:05Z

When scan_swap_map() finds a free cluster of swap pages to allocate, discard the old contents of the cluster if the device supports discard. But don't bother when swap is so fragmented that we allocate single pages. Be careful about racing allocations made while we're scanning for a cluster; and hold up allocations made while we're discarding. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Cc: David Woodhouse Cc: Jens Axboe Cc: Matthew Wilcox Cc: Joern Engel Cc: James Bottomley Cc: Donjun Shin Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swapfile: swapon use discard (trim)

2009-01-06T23:59:05Z

When adding swap, all the old data on swap can be forgotten: sys_swapon() discard all but the header page of the swap partition (or every extent but the header of the swap file), to give a solidstate swap device the opportunity to optimize its wear-levelling. If that succeeds, note SWP_DISCARDABLE for later use, and report it with a "D" at the right end of the kernel's "Adding ... swap" message. Perhaps something should be shown in /proc/swaps (swapon -s), but we have to be more cautious before making any addition to that format. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Cc: David Woodhouse Cc: Jens Axboe Cc: Matthew Wilcox Cc: Joern Engel Cc: James Bottomley Cc: Donjun Shin Cc: Tejun Heo Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swapfile: rearrange scan and swap_info

2009-01-06T23:59:05Z

Before making functional changes, rearrange scan_swap_map() to simplify subsequent diffs. Actually, there is one functional change in there: leave cluster_nr negative while scanning for a new cluster - resetting it early increased the likelihood that when we have difficulty finding a free cluster, another task may come in and try doing exactly the same - just a waste of cpu. Before making functional changes, rearrange struct swap_info_struct slightly: flags will be needed as an unsigned long (for wait_on_bit), next is a good int to pair with prio, old_block_size is uninteresting so shift it to the end. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds

swapfile: remove SWP_ACTIVE mask

2009-01-06T23:59:05Z

Remove the SWP_ACTIVE mask: it just obscures the SWP_WRITEOK flag. Signed-off-by: Hugh Dickins Cc: KAMEZAWA Hiroyuki Cc: Nick Piggin Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds