Message ID | 20130522004541.GA17240@obelix.rh |
---|---|
State | RFC, archived |
Delegated to: | David Miller |
Headers | show |
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@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, May 21, 2013 at 06:09:22PM -0700, Eric Dumazet wrote: > On Tue, 2013-05-21 at 21:45 -0300, Flavio Leitner wrote: > > 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 ? So far there is no other problem besides the weird tcp_wmem. > Wouldn't be easier to chose 4096 on all arches ? Not sure what you're referring to. That config comes from a distro kernel, so it's not under my control. If it is about the upper limit for sk_mem_quantum, 4k seems enough to me as well. > Are you sure a network driver doesn't provide skb using a full page ? You lost me. You're saying that today we consider a page size a minimum and so if we reduce that, the skb wouldn't fit in the min sk memory? Thanks,
On Tue, 2013-05-21 at 22:58 -0300, Flavio Leitner wrote: > On Tue, May 21, 2013 at 06:09:22PM -0700, Eric Dumazet wrote: > > > Are you sure a network driver doesn't provide skb using a full page ? > > You lost me. You're saying that today we consider a page size > a minimum and so if we reduce that, the skb wouldn't fit in the > min sk memory? SK_MEM_QUANTUM is also used in UDP stack, thats why I am asking. -- To unsubscribe from this list: send the line "unsubscribe netdev" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
On Tue, May 21, 2013 at 07:21:01PM -0700, Eric Dumazet wrote: > On Tue, 2013-05-21 at 22:58 -0300, Flavio Leitner wrote: > > On Tue, May 21, 2013 at 06:09:22PM -0700, Eric Dumazet wrote: > > > > > Are you sure a network driver doesn't provide skb using a full page ? > > > > You lost me. You're saying that today we consider a page size > > a minimum and so if we reduce that, the skb wouldn't fit in the > > min sk memory? > > SK_MEM_QUANTUM is also used in UDP stack, thats why I am asking. Yeah, it is. SCTP too, but for the protocol cases, the most complex one appears to be TCP, and it doesn't seem to be a problem to replace the minimum with something not page sized. For the drivers, it seems to have an indirect assumption that page size bytes is a minimum acceptable, so changing this minimum could cause a performance issue. Well, this define is quite old, so I am not sure if there are other historical reasons to keep it page size. However, if the idea of fixing SK_MEM_QUANTUM to 4k seems reasonable, I am willing to spend more time digging into this. Thanks!
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