From: Eric Dumazet <eduma...@google.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, giving suboptimal TCP performance
since windows are lowered to ridiculous values.
Note that sysctl_mem units being in pages and in ABI, we also need
to change sk_prot_mem_limits() accordingly.
Signed-off-by: Eric Dumazet <eduma...@google.com>
---
include/net/sock.h | 23 +++++++++++++++++------
1 file changed, 17 insertions(+), 6 deletions(-)
diff --git a/include/net/sock.h b/include/net/sock.h
index
f13ac87a8015cb18c5d3fe5fdcf2d6a0592428f4..d904d1835e06c970fea958c048d927137171477f
100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -1162,11 +1162,6 @@ static inline void sk_enter_memory_pressure(struct sock
*sk)
sk->sk_prot->enter_memory_pressure(sk);
}
-static inline long sk_prot_mem_limits(const struct sock *sk, int index)
-{
- return sk->sk_prot->sysctl_mem[index];
-}
-
static inline long
sk_memory_allocated(const struct sock *sk)
{
@@ -1281,11 +1276,27 @@ 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
+/* sysctl_mem values are in pages, we convert them in SK_MEM_QUANTUM units */
+static inline long sk_prot_mem_limits(const struct sock *sk, int index)
+{
+ long val = sk->sk_prot->sysctl_mem[index];
+
+#if PAGE_SIZE > SK_MEM_QUANTUM
+ val <<= PAGE_SHIFT - SK_MEM_QUANTUM_SHIFT;
+#elif PAGE_SIZE < SK_MEM_QUANTUM
+ val >>= SK_MEM_QUANTUM_SHIFT - PAGE_SHIFT;
+#endif
+ return val;
+}
+
static inline int sk_mem_pages(int amt)
{
return (amt + SK_MEM_QUANTUM - 1) >> SK_MEM_QUANTUM_SHIFT;
