Messages in this thread |  | | Date | Mon, 4 Jul 2022 12:38:46 +0900 | From | Dominique Martinet <> | Subject | Re: [PATCH 3/3] 9p: Add mempools for RPCs |
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+Christian, sorry I just noticed you weren't in Ccs again -- the patches are currently there if you want a look: https://evilpiepirate.org/git/bcachefs.git/log/?h=9p_mempool
I think it'll conflict a bit with your 8k non-read/write RPCs but I'll take care of that when checking it this weekend.
Kent Overstreet wrote on Sun, Jul 03, 2022 at 11:05:57PM -0400: > > We shouldn't have any user calling with more at this point (the > > user-provided size comes from p9_client_prepare_req arguments and it's > > either msize or header size constants); and it probably makes sense to > > check and error out rather than cap it. > > If that's the case I think we should just switch the warning to a BUG_ON() - I > just wasn't sure from reading the code if that was really guarded against.
yes, BUG_ON is good for me.
> > > - if (p9_fcall_init(c, &req->tc, alloc_msize)) > > > + if (p9_fcall_init(c, &req->tc, 0, alloc_msize)) > > > goto free_req; > > > - if (p9_fcall_init(c, &req->rc, alloc_msize)) > > > + if (p9_fcall_init(c, &req->rc, 1, alloc_msize)) > > > > given the two rc/tc buffers are of same size I don't see the point of > > using two caches either, you could just double the min number of > > elements to the same effect? > > You can't double allocate from the same mempool, that will deadlock if multiple > threads need the last element at the same time - I should've left a comment for > that.
hmm, looking at the code as long as min elements is big enough the deadlock becomes increasingly difficult to hit -- but I guess there's no guarantee we won't get 8 threads each getting their first item from the pool and starving each other on the second... Fair enough, thank you for the comment.
> @@ -270,10 +276,8 @@ p9_tag_alloc(struct p9_client *c, int8_t type, unsigned int max_size) > if (!req) > return ERR_PTR(-ENOMEM); > > - if (p9_fcall_init(c, &req->tc, alloc_msize)) > - goto free_req; > - if (p9_fcall_init(c, &req->rc, alloc_msize)) > - goto free; > + p9_fcall_init(c, &req->tc, 0, alloc_msize); > + p9_fcall_init(c, &req->rc, 1, alloc_msize);
mempool allocation never fails, correct?
(don't think this needs a comment, just making sure here)
This all looks good to me, will queue it up in my -next branch after running some tests next weekend and hopefully submit when 5.20 opens with the code making smaller allocs more common.
-- Dominique
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