Messages in this thread | | | Subject | Re: [PATCH 0/1] ipc/util.{c,h}: Use binary search for max_idx | From | Manfred Spraul <> | Date | Sun, 25 Apr 2021 20:19:51 +0200 |
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Hi Davidlohr,
On 4/25/21 8:07 PM, Davidlohr Bueso wrote: > On Sun, 25 Apr 2021, Manfred Spraul wrote: > >> 2nd version of the patch: >> @Andrew: Could you add the patch to your mm tree, as candidate for >> linux-next? >> >> Note: >> I have tried to remove the ids->max_idx cache entirely. Unfortunately, >> this causes a significant slow-down of semstat(,,IPC_STAT): >> * no object allocated, no ipcmni_extended: +50% >> * no object allocated, with ipcmni_extended: +80% >> * 30 objects allocated, with large gaps, no ipcmni_extended: >> +350% >> Thus I haven't removed ids->max_id. > > Right, IPC_STAT is the main usecase for max_id. But I'm not sure why > you were looking to remove it in the first place - or was it just to > avoid this patch altogether? > I had assumed that after removing the linear search, the lookup would be so fast that the cache can be removed entirely. It would save ~20 lines of code and one int in struct ipc_ids (12 bytes per namespace?).
But: My assumption was wrong, the slowdown is too large.
--
Manfred
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