2011-07-28 (목), 16:21 -0400, Jeff Moyer: > Hi, > > Sorry, I don't have the original posting of this message, so I've just > cut-n-paste from the archives on lkml.org: > https://lkml.org/lkml/2011/6/1/235 > Hello, Jeff. Thanks for finding and replying to this :) > The proposal was this: > > > Add FLUSH/FUA support to blktrace. As FLUSH precedes WRITE and/or > > FUA follows WRITE, use the same 'F' flag for both cases and > > distinguish them by their (relative) position. The end results > > look like (other flags might be shown also): > > > > - WRITE: W > > - WRITE_FLUSH: FW > > - WRITE_FUA: WF > > - WRITE_FLUSH_FUA: FWF > > I'm not sure I'll ever be able to keep that straight. How about we use > 'F' for FUA, since FUA is capitalized anyway, and use 'f' for flush? > Too subtle? > Either way is fine to me. Jens? > Next... > > > @@ -14,7 +14,7 @@ > > enum blktrace_cat { > > BLK_TC_READ = 1 << 0, /* reads */ > > BLK_TC_WRITE = 1 << 1, /* writes */ > > - BLK_TC_BARRIER = 1 << 2, /* barrier */ > > + BLK_TC_FUA = 1 << 2, /* fua requests */ > > I would prefer to replace BARRIER with FLUSH, as I think they are closer > relatives. Doing it the way you've suggested would mean that older > blktrace user-space would report FUA as a Barrier. > I thought about that too. But as I said in the changelog, it led to a negative number at the rhs of MASC_TC_BIT calculation, so the end result was not good. In the meantime, I found that Matthew Wilcox posted a patch which relocates some REQ_ flags to appropriate positions. https://lkml.org/lkml/2011/6/2/324 With the patch, it seems ok to replace BARRIER with FLUSH. However it looks like the patch isn't included into the tree yet. BTW, I'm thinking about user-space again. I'm not sure it's ok if older blktrace tool reports FLUSH/FUA as BARRIER. Actually I posted a patch that treats FLUSH as BARRIER [1], and Jens and others commented we should not do that. To end that, I could leave BLK_TC_BARRIER as is, and add BLK_TC_{FLUSH,FUA} at the end of blktrace_cat. But as we exhause space in the 16-bit act_mask, it would require a substantial change. Any thoughts? > Comments? No matter what's agreed upon, we should get this in sooner > rather than later, as it's a big missing piece in trying to diagnose > performance issues! > > Cheers, > Jeff Thanks. [1] https://lkml.org/lkml/2011/5/27/206 -- Regards, Namhyung Kim -- To unsubscribe from this list: send the line "unsubscribe linux-btrace" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
