Re: [PATCH] 2.2.17pre7 VM enhancement Re: I/O performance on

[Andrea Arcangeli]

On Wed, 28 Jun 2000, Marcelo Tosatti wrote:

>Innocent processes (e.g. syslogd, klogd, bash) are getting killed
>with this patches. 

While you are oom, or while you're running mmap002, right? If so that's
intentional and I'm very aware of the MAP_SHARED problem but what we did
so far to fix that MAP_SHARED issue is band-aid (that could hurt the other
cases that works right). I believe that the real problem of MAP_SHARED is
that we don't know anything about the state of the pages in MAP_SHARED
segment. We consider all them as clean without doing any write throttling
and we allow the VM to become fully dirty; while for good reasons in the
rest of the kernel we instead assume that there is a max percentage of the
RAM that could become dirty at the same time.

Then there is the fact that the VM isn't handling gracefully the case
where all the memory is dirty, that's another issue and it's secondary
problem IMHO (all the VM shouldn't become dirty so easily as now in first
place).

Andrea