The current tcp_mem initialization gives values that are really too
small for systems with ~256-768 MB of memory, and also for systems with
larger page sizes (ia64). This patch gives an alternate method of
initialization that doesn't depend on the cache allocation functions,
but I think should still provide a nice curve that gives a smaller
fraction of total memory with small-memory systems, while maintaining
the same upper bound (pressure at 1/2, max as 3/4) on larger memory systems.
-John
Change tcp_mem initialization function. The fraction of total memory is now
a continuous function of memory size, and independent of page size.
Signed-off-by: John Heffner <[EMAIL PROTECTED]>
---
commit a4461a36efb376bf01399cfd6f1ad15dc89a8794
tree 23b2fb9da52b45de8008fc7ea6bb8c10e3a3724b
parent 8b9909ded6922c33c221b105b26917780cfa497d
author John Heffner <[EMAIL PROTECTED]> Wed, 14 Mar 2007 17:15:06 -0400
committer John Heffner <[EMAIL PROTECTED]> Wed, 14 Mar 2007 17:15:06 -0400
net/ipv4/tcp.c | 13 ++++++++++---
1 files changed, 10 insertions(+), 3 deletions(-)
diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
index 74c4d10..3834b10 100644
--- a/net/ipv4/tcp.c
+++ b/net/ipv4/tcp.c
@@ -2458,11 +2458,18 @@ void __init tcp_init(void)
sysctl_max_syn_backlog = 128;
}
- /* Allow no more than 3/4 kernel memory (usually less) allocated to TCP
*/
- sysctl_tcp_mem[0] = (1536 / sizeof (struct inet_bind_hashbucket)) <<
order;
- sysctl_tcp_mem[1] = sysctl_tcp_mem[0] * 4 / 3;
+ /* Set the pressure threshold to be a fraction of global memory that
+ * is up to 1/2 at 256 MB, decreasing toward zero with the amount of
+ * memory, with a floor of 128 pages.
+ */
+ limit = min(nr_all_pages, 1UL<<(28-PAGE_SHIFT)) >> (20-PAGE_SHIFT);
+ limit = (limit * (nr_all_pages >> (20-PAGE_SHIFT))) >> (PAGE_SHIFT-11);
+ limit = max(limit, 128UL);
+ sysctl_tcp_mem[0] = limit / 4 * 3;
+ sysctl_tcp_mem[1] = limit;
sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;
+ /* Set per-socket limits to no more than 1/128 the pressure threshold */
limit = ((unsigned long)sysctl_tcp_mem[1]) << (PAGE_SHIFT - 7);
max_share = min(4UL*1024*1024, limit);
