Kyle Moffett wrote:
On Jun 28, 2007, at 14:49:24, Davide Libenzi wrote:
I was using oprofile to sample some userspace code I am working on,
and I was continuosly noticing clear_page in the top three entries
of the oprofile logs.
Also, a simple kernel build, in my Dual Opteron with 8GB of RAM,
shows clear_page as the first kernel entry, second only to the
userspace the cc1 and as. Most of the userspace code uses malloc()
(and anonymous mappings) in such a way that the memory returned via
kernel->glibc is immediately written soon after. The POSIX malloc()
definition itself also, does not require the returned memory to be
zeroed (as calloc() does).
So I implemented a rather quick hack that introduces a new mmap() flag
MAP_NOZERO (only valid for anonymous mappings) and the vma
counter-part VM_NOZERO. Also, a new sys_brk2() has been introduced to
accept a new flags parameter. A brief description of the patches
follows in the next emails.
Hmm, sounds like this would also need a "MAP_NOREUSE" flag of some kind
for security sensitive applications.
That wants MAP_PRIVATE so that the kernel can also decide to not
swap these pages out to an unencrypted swap area.
--
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is. Each group
calls the other unpatriotic.
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