On Wed, 2014-06-25 at 10:25 +0200, Thomas Knauth wrote: > On Wed, Jun 25, 2014 at 8:25 AM, Artem Bityutskiy <dedekind1@xxxxxxxxx> wrote: > > Plus some explanations WRT why proc-based interface and what would be > > the alternatives, what if tomorrow we want to extend the functionality > > and drop caches only for certain file range, is this only for regular > > files or also for directories, why posix_fadvice(DONTNEED) is not > > sufficient. > > I suggested the idea originally. Let me address each of your questions in turn: Thanks for the answer, although you forgot to comment on the question about possibly extending the new interface to work with file ranges in the future. For example, I have a 2 TiB file, and I am only interested in dropping caches for the first couple of gigabytes. Would I extend your interface, or would I come up with another one? > Why a selective drop? To have a middle ground between echo 2 > > drop_caches and echo 3 > drop_caches. When is this interesting? My > particular use case was benchmarking. I wanted to repeatedly measure > the timing when things were read from disk. Dropping everything from > the cache, also drops useful things, not just the few files your > benchmark intends to measure. Sounds like a reasonable motivation for me. > Why /proc? Because this is where the current drop_caches mechanism is > located. If it should go somewhere else, please do suggest so. I do not have particular suggestions, just pulling the information about how much efforts were put into choosing the interface. > Why not use posix_fadvice()? Because it is exactly this, an advice. > The kernel is free to do whatever, i.e., also ignore the request. We > want a mechanism that reliably drops select content from the cache. OK, thanks. -- Best Regards, Artem Bityutskiy -- To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
