This is a hack against 3.10.y to see if using cached allocations works better here. The unintended consequence is in the reference benchmark case, it performs ~7% better than the existing code even with a hacked slower get_page()/put_page(). The intent was to avoid very slow order-3 allocations (and really pathological retries under failure) which can cause lots of problems from OOM killer invocation to direct reclaim/compaction cycles that take up nearly all cpu and end up reaping large amounts of page cache which would have been otherwise useful. This is a regression from the same code that used order-0 allocations since those are easy and fast as they are cached per-cpu, and this code is under very heavy alloc/free behavior. This patch eliminates a majority of that due to slab caching the allocations, though could still be improved by slab holding onto free'd slabs longer; this seems like an unoptimized case when object size == slab size. vmstat output of bad behavior: http://pastebin.ubuntu.com/6687527/ This patchset could be fixed for submission by either making another pool of cached frag buffers specifically page_frag (not using slab), or by converting the whole stack to not use get_page/put_page() to reference count and free page allocations so that hacking swap.c is not necessary and slab use normal. Benchmark: ifconfig lo mtu 16436 perf record ./netperf -t UDP_STREAM ; perf report With order-0 allocations: UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost (127.0.0.1) port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 262144 65507 10.00 820758 0 43012.26 262144 10.00 820754 43012.05 # Overhead Command Shared Object Symbol # ........ ....... ................. .......................................... # 46.15% netperf [kernel.kallsyms] [k] copy_user_generic_string 7.89% netperf [kernel.kallsyms] [k] skb_append_datato_frags 6.06% netperf [kernel.kallsyms] [k] get_page_from_freelist 3.87% netperf [kernel.kallsyms] [k] __rmqueue 1.36% netperf [kernel.kallsyms] [k] __alloc_pages_nodemask 1.11% netperf [kernel.kallsyms] [k] alloc_pages_current linux-3.10.y stock order-3 allocations: UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost (127.0.0.1) port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 65507 10.00 1054158 0 55243.69 212992 10.00 1019505 53427.68 # Overhead Command Shared Object Symbol # ........ ....... ................. .......................................... # 59.80% netperf [kernel.kallsyms] [k] copy_user_generic_string 2.35% netperf [kernel.kallsyms] [k] get_page_from_freelist 1.95% netperf [kernel.kallsyms] [k] skb_append_datato_frags 1.27% netperf [ip_tables] [k] ipt_do_table 1.26% netperf [kernel.kallsyms] [k] udp_sendmsg 1.03% netperf [kernel.kallsyms] [k] enqueue_task_fair 1.00% netperf [kernel.kallsyms] [k] ip_finish_output With this patchset: UDP UNIDIRECTIONAL SEND TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET to localhost (127.0.0.1) port 0 AF_INET Socket Message Elapsed Messages Size Size Time Okay Errors Throughput bytes bytes secs # # 10^6bits/sec 212992 65507 10.00 1127089 0 59065.70 212992 10.00 1072997 56230.98 # Overhead Command Shared Object Symbol # ........ ....... ................. .......................................... # 69.16% netperf [kernel.kallsyms] [k] copy_user_generic_string 2.56% netperf [kernel.kallsyms] [k] skb_append_datato_frags 1.00% netperf [ip_tables] [k] ipt_do_table 0.96% netperf [kernel.kallsyms] [k] sock_alloc_send_pskb 0.93% netperf [kernel.kallsyms] [k] _raw_spin_lock -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>