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SubjectRe: [PFC]: hash instrumentation
On Sat, 10 Apr 1999, Chuck Lever wrote:

>i think that's the key. moving this bit of code from getblk() to
>find_buffer() is a measureable slowdown, it turns out:

Really I was talking about my lru_cache_mkyoung() (that replaced
setbit(PG_referenced)), but yes, the put_last_lru() performance-hurt issue
is equivalent.

>i removed it completely (along with put_last_lru() since now no-one uses
>it), since these lists are no longer LRU, and found that performance

I just noticed in the last days that nobody seems using the lru-buffer
information. Right now it looks like to me that you are perfectly right.

>but this also means that you should be *very* careful where you put your
>"touch_buffer(bh)" because you don't want that in a performance path like
>find_buffer(). leaving touch_buffer() in bread() and brw_page() might be

Hmm, yes probably this is a good idea, I'll think about that tomorrow.
Thanks!!

Andrea Arcangeli


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