Hi Davidlohr,
On 04/03/2014 02:20 AM, Davidlohr Bueso wrote:
The default size for shmmax is, and always has been, 32Mb.
Today, in the XXI century, it seems that this value is rather small,
making users have to increase it via sysctl, which can cause
unnecessary work and userspace application workarounds[1].
Instead of choosing yet another arbitrary value, larger than 32Mb,
this patch disables the use of both shmmax and shmall by default,
allowing users to create segments of unlimited sizes. Users and
applications that already explicitly set these values through sysctl
are left untouched, and thus does not change any of the behavior.
So a value of 0 bytes or pages, for shmmax and shmall, respectively,
implies unlimited memory, as opposed to disabling sysv shared memory.
This is safe as 0 cannot possibly be used previously as SHMMIN is
hardcoded to 1 and cannot be modified.
Are we sure that no user space apps uses shmctl(IPC_INFO) and prints a
pretty error message if shmall is too small?
We would break these apps.
--
Manfred
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