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* The value of FB_MTU eats two pages
@ 2021-06-01 14:18 Menglong Dong
  2021-06-02 19:50 ` Jon Maloy
  0 siblings, 1 reply; 5+ messages in thread
From: Menglong Dong @ 2021-06-01 14:18 UTC (permalink / raw)
  To: jmaloy
  Cc: ying.xue, David Miller, Jakub Kicinski, etdev, tipc-discussion, LKML


I have a question about the value of FB_MTU in tipc, how does the '3744' form?
I notice that it is used in 'tipc_msg_build()' when memory allocation
fails, and it
tries to fall back to a smaller MTU to avoid unnecessary sending failures.

However, the size of the data allocated will be more than 4096 when FB_MTU
is 3744. I did a rough calculation, the size of data will more than 4200:

(FB_MTU + TIPCHDR + BUF_HEADROOM + sizeof(struct skb_shared_info))

Therefore, 8192 will be allocated from slab, and about 4000 of it will
not be used.

FB_MTU is used for low memory, and I think eating two pages will make it worse.
Do I miss something?

Menglong Dong

^ permalink raw reply	[flat|nested] 5+ messages in thread

end of thread, other threads:[~2021-06-03 14:56 UTC | newest]

Thread overview: 5+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2021-06-01 14:18 The value of FB_MTU eats two pages Menglong Dong
2021-06-02 19:50 ` Jon Maloy
2021-06-03  2:26   ` Menglong Dong
2021-06-03 13:08     ` Jon Maloy
2021-06-03 14:54       ` Menglong Dong

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