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authorEric Dumazet <edumazet@google.com>2019-06-14 16:22:21 -0700
committerDavid S. Miller <davem@davemloft.net>2019-06-14 20:18:28 -0700
commitce27ec60648d8e066227cb2f58b1d3d4f7253d08 (patch)
tree220daaf7fb72acc2cfe6fab06c1ac0e0f4384157 /net/core/sock.c
parenttcp: add tcp_tx_skb_cache sysctl (diff)
downloadlinux-dev-ce27ec60648d8e066227cb2f58b1d3d4f7253d08.tar.xz
linux-dev-ce27ec60648d8e066227cb2f58b1d3d4f7253d08.zip
net: add high_order_alloc_disable sysctl/static key
>From linux-3.7, (commit 5640f7685831 "net: use a per task frag allocator") TCP sendmsg() has preferred using order-3 allocations. While it gives good results for most cases, we had reports that heavy uses of TCP over loopback were hitting a spinlock contention in page allocations/freeing. This commits adds a sysctl so that admins can opt-in for order-0 allocations. Hopefully mm layer might optimize order-3 allocations in the future since it could give us a nice boost (see 8 lines of following benchmark) The following benchmark shows a win when more than 8 TCP_STREAM threads are running (56 x86 cores server in my tests) for thr in {1..30} do sysctl -wq net.core.high_order_alloc_disable=0 T0=`./super_netperf $thr -H 127.0.0.1 -l 15` sysctl -wq net.core.high_order_alloc_disable=1 T1=`./super_netperf $thr -H 127.0.0.1 -l 15` echo $thr:$T0:$T1 done 1: 49979: 37267 2: 98745: 76286 3: 141088: 110051 4: 177414: 144772 5: 197587: 173563 6: 215377: 208448 7: 241061: 234087 8: 267155: 263373 9: 295069: 297402 10: 312393: 335213 11: 340462: 368778 12: 371366: 403954 13: 412344: 443713 14: 426617: 473580 15: 474418: 507861 16: 503261: 538539 17: 522331: 563096 18: 532409: 567084 19: 550824: 605240 20: 525493: 641988 21: 564574: 665843 22: 567349: 690868 23: 583846: 710917 24: 588715: 736306 25: 603212: 763494 26: 604083: 792654 27: 602241: 796450 28: 604291: 797993 29: 611610: 833249 30: 577356: 841062 Signed-off-by: Eric Dumazet <edumazet@google.com> Signed-off-by: David S. Miller <davem@davemloft.net>
Diffstat (limited to 'net/core/sock.c')
-rw-r--r--net/core/sock.c4
1 files changed, 3 insertions, 1 deletions
diff --git a/net/core/sock.c b/net/core/sock.c
index 2b3701958486..7f49392579a5 100644
--- a/net/core/sock.c
+++ b/net/core/sock.c
@@ -2320,6 +2320,7 @@ static void sk_leave_memory_pressure(struct sock *sk)
/* On 32bit arches, an skb frag is limited to 2^15 */
#define SKB_FRAG_PAGE_ORDER get_order(32768)
+DEFINE_STATIC_KEY_FALSE(net_high_order_alloc_disable_key);
/**
* skb_page_frag_refill - check that a page_frag contains enough room
@@ -2344,7 +2345,8 @@ bool skb_page_frag_refill(unsigned int sz, struct page_frag *pfrag, gfp_t gfp)
}
pfrag->offset = 0;
- if (SKB_FRAG_PAGE_ORDER) {
+ if (SKB_FRAG_PAGE_ORDER &&
+ !static_branch_unlikely(&net_high_order_alloc_disable_key)) {
/* Avoid direct reclaim but allow kswapd to wake */
pfrag->page = alloc_pages((gfp & ~__GFP_DIRECT_RECLAIM) |
__GFP_COMP | __GFP_NOWARN |