Trond Myklebust wrote:
On Wed, 2006-12-13 at 12:56 +1100, Nick Piggin wrote:
Note that these pages should be *really* rare. Definitely even for normal
filesystems I think RMW would use too much bandwidth if it were required
for any significant number of writes.
If file "foo" exists on the server, and contains data, then something
like
fd = open("foo", O_WRONLY);
write(fd, "1", 1);
should never need to trigger a read. That's a fairly common workload
when you think about it (happens all the time in apps that do random
write).
I have to admit that I've only been paying attention with one eye, but
why doesn't this require a read? If "foo" is non-zero in size, then
how does the client determine how much data in the buffer to write to
the server?
Isn't RMW required for any i/o which is either not buffer aligned or
a multiple of the buffer size?
Thanx...
ps
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