netdev - [PATCH net-next] net: set SK_MEM

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Message-ID: <1477940320.7065.312.camel@edumazet-glaptop3.roam.corp.google.com>
Date:   Mon, 31 Oct 2016 11:58:40 -0700
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     David Miller <davem@...emloft.net>
Cc:     netdev <netdev@...r.kernel.org>,
        Neal Cardwell <ncardwell@...gle.com>,
        Yuchung Cheng <ycheng@...gle.com>
Subject: [PATCH net-next] net: set SK_MEM_QUANTUM to 4096

From: Eric Dumazet <edumazet@...gle.com>

Systems with large pages (64KB pages for example) do not always have
huge quantity of memory.

A big SK_MEM_QUANTUM value leads to fewer interactions with the
global counters (like tcp_memory_allocated) but might trigger
memory pressure much faster, thus suboptimal TCP performance
since windows are lowered to ridiculous values.

Signed-off-by: Eric Dumazet <edumazet@...gle.com>
---
 include/net/sock.h |    5 ++++-
 1 file changed, 4 insertions(+), 1 deletion(-)

diff --git a/include/net/sock.h b/include/net/sock.h
index f13ac87a8015cb18c5d3fe5fdcf2d6a0592428f4..d3409bb514e7f08b9cf183b7405d876bec18d732 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1281,7 +1281,10 @@ int __sk_mem_schedule(struct sock *sk, int size, int kind);
 void __sk_mem_reduce_allocated(struct sock *sk, int amount);
 void __sk_mem_reclaim(struct sock *sk, int amount);
 
-#define SK_MEM_QUANTUM ((int)PAGE_SIZE)
+/* We used to have PAGE_SIZE here, but systems with 64KB pages
+ * do not necessarily have 16x time more memory than 4KB ones.
+ */
+#define SK_MEM_QUANTUM 4096
 #define SK_MEM_QUANTUM_SHIFT ilog2(SK_MEM_QUANTUM)
 #define SK_MEM_SEND	0
 #define SK_MEM_RECV	1