Messages in this thread | | | Date | Sun, 14 Jun 2009 21:34:19 +0900 (JST) | Subject | Re: NILFS2 get stuck after bio_alloc() fail | From | Ryusuke Konishi <> |
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Hi, On Sun, 14 Jun 2009 10:00:06 +0300, Pekka Enberg <penberg@cs.helsinki.fi> wrote: > On Sun, Jun 14, 2009 at 9:30 AM, Ryusuke > Konishi<konishi.ryusuke@lab.ntt.co.jp> wrote: >> The original GFP flag was GFP_NOIO, but replaced to GFP_NOWAIT at a >> preliminary release in February 2008. It was because a user >> experienced system memory shortage by the bio_alloc() call. >> >> Even though nilfs_alloc_seg_bio() repeatedly calls bio_alloc() >> reducing the number of bio vectors in case of failure, this fallback >> did not work well. >> >> I'm in two minds whether I should change it back to GFP_NOIO. >> Or should I switch the gfp as follows? > > As far as I can tell, the only difference with GFP_NOIO and GFP_NOWAIT > here is that the former will trigger the mempool_alloc() page reclaim > path. But I am not sure I understand why switching to GFP_NOWAIT > helped with memory shortage. What exactly was the problem there? > > Pekka
I will confirm the details later. I cannot dig into the record due to planned outage at office now. The version I replaced GFP_NOIO with GFP_NOWAIT is considerably old. A true problem might have been in other places somewhere.
For reference, the retry loop in question is as follows. It is to allocate bio for log writing.
bio = bio_alloc(GFP_NOWAIT, nr_vecs); if (bio == NULL) { while (!bio && (nr_vecs >>= 1)) bio = bio_alloc(GFP_NOWAIT, nr_vecs); }
where nr_vecs is less than or equal to bio_get_nr_vecs(bdev).
Thanks, Ryusuke Konishi -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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