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Date: Tue, 21 May 2013 18:09:22 -0700 From: Eric Dumazet <eric.dumazet@...il.com> To: Flavio Leitner <fbl@...hat.com> Cc: netdev@...r.kernel.org, David Miller <davem@...emloft.net> Subject: Re: RFC limit sk_mem_quantum to 8192 On Tue, 2013-05-21 at 21:45 -0300, Flavio Leitner wrote: > Hi, > > The page size can be 64k on ppc64, so SK_MEM_QUANTUM increases to > that value as well. > > net/ipv4/tcp.c: > ... > sysctl_tcp_wmem[0] = SK_MEM_QUANTUM; > sysctl_tcp_wmem[1] = 16*1024; > sysctl_tcp_wmem[2] = max(64*1024, max_share); > > sysctl_tcp_rmem[0] = SK_MEM_QUANTUM; > sysctl_tcp_rmem[1] = 87380; > sysctl_tcp_rmem[2] = max(87380, max_share); > > and: > include/net/sock.h: > #define SK_MEM_QUANTUM ((int)PAGE_SIZE) > > ppc64 config: > # CONFIG_PPC_4K_PAGES is not set > # CONFIG_PPC_16K_PAGES is not set > CONFIG_PPC_64K_PAGES=y > # CONFIG_PPC_256K_PAGES is not set > > It seems too much for a minimum reserved memory. Also, the > other values are meaningless in this case because default > is only 16k and the maximum is limited to 64k. > > This will require a modification in the > Documentation/networking/ip-sysctl.txt as well which states > that default minimum is 1 page. > > Also, sk_mem_schedule() and friends will have to consider > that SK_MEM_QUANTUM might not be PAGE_SIZE anymore. > > Well, the patch below illustrates what I am talking. > thanks, > fbl > > diff --git a/include/net/sock.h b/include/net/sock.h > index 5d84de4..d52fa2d 100644 > --- a/include/net/sock.h > +++ b/include/net/sock.h > @@ -954,7 +954,12 @@ static inline struct inode *SOCK_INODE(struct socket *socket) > extern int __sk_mem_schedule(struct sock *sk, int size, int kind); > extern void __sk_mem_reclaim(struct sock *sk); > > +#if PAGE_SIZE < 8192 > #define SK_MEM_QUANTUM ((int)PAGE_SIZE) > +#else > +#define SK_MEM_QUANTUM ((int)8192) > +#endif > + > #define SK_MEM_QUANTUM_SHIFT ilog2(SK_MEM_QUANTUM) > #define SK_MEM_SEND 0 > #define SK_MEM_RECV 1 > What particular problem do you want to solve ? Wouldn't be easier to chose 4096 on all arches ? Are you sure a network driver doesn't provide skb using a full page ? -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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