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Re: [dm-devel] [PATCH] DM-CRYPT: Scale to multiple CPUs

, Mikulas Patocka wrote:

If you are optimizing it,

1) why don't you optimize it in such a way that if one CPU submits
requests, the crypto work is spread among all the CPUs? Currently it
spreads the work only if different CPUs submit it.

This case is only useful with very slow CPUs and is handled by pcrypt
in theory

(but I haven't tested it)

2) why not optimize software async crypto daemon (crypt/cryptd.c) instead
of dm-crypt, so that all kernel subsystems can actually take advantage of
those multi-CPU optimizations, not just dm-crypt?

Normally most subsystems are multi-CPU already, unless they limit
themselves artitifically like dm-crypt.

For dm-crypt would be wasteful to funnel everything through two single CPU threads just
to spread it out again.  That is why I also used per CPU IO threads too.


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