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Re: [Xen-devel] [RFC PATCH] xs: use system's default stack size for xs_watch's reader thread

On Wed, Sep 21, 2016 at 9:00 AM, Wei Liu <wei.liu2@xxxxxxxxxx> wrote:
> On Wed, Sep 21, 2016 at 08:51:07AM -0400, Konrad Rzeszutek Wilk wrote:
>> On Tue, Sep 20, 2016 at 05:29:39PM -0400, Chris Patterson wrote:
>> > From: Chris Patterson <pattersonc@xxxxxxxxxxxx>
>> >
>> > xs_watch() creates a thread to listen to xenstore events.  Currently, the
>> > thread is created with the greater of 16K or PTHREAD_MIN_SIZE.
>> >
>> > There have been several bug reports and workarounds related to the issue
>> > where xs_watch() fails because its attempt to create the reader thread with
>> > pthread_create() fails. This is due to insufficient stack space size
>> > given the requirements for thread-local storage usage in the applications
>> > and libraries that are linked against libxenstore.  [1,2,3,4].
>> >
>> > Specifying the stack size appears to have been added to reduce memory
>> > footprint (1d00c73b983b09fbee4d9dc0f58f6663c361c345).
>> Ugh. 8MB.
> OOI isn't that 8MB virtual memory, which means it shouldn't have real
> impact unless it is used?

From what I understand, that is correct.  At least in the Linux/glibc
case, I believe the stack is allocated using anonymous mmap() and that
resident memory usage shouldn't be greater than what you actually end
up writing.  However, I do not know if this holds true universally...

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