[M3devel] thread local storage, but in C pieces of runtime... (jay, tony?)

Mon May 13 02:48:34 CEST 2013

Yes, it will vary by OS and hardware platform.
I don’t know how good they are on modern systems, but I do believe a C compiler will do a better job with whatever intrinsics it supports for thread-locals.
See http://en.cppreference.com/w/c/thread for the C11 intrinsics.

On May 11, 2013, at 1:22 AM, mika at async.caltech.edu wrote:

> This is just one data point, but I remember testing the performance of thread locals
> on pthreads, probably on an old FreeBSD system, and the performance was horrendously
> bad.  There was a system call involved in obtaining the pointer to the thread-local
> area.  I was had some clever algorithms I wanted to use thread locals for (since you
> can do all sorts of things without locks then), but I gave up on it since it was way
> more expensive than a lock on that system...
> 
>     Mika
> 
> =?utf-8?Q?Dragi=C5=A1a_Duri=C4=87?= writes:
>> 
>> --Apple-Mail=_EEF8E283-B126-4B87-BA54-81432C085954
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>> It probably does=E2=80=A6 Because our interface to pthread specifics is =
>> surely not inlined, and sp hacks most probably are. Still, to access =
>> this C code, a procedure call is inserted=E2=80=A6 If sp hack is more =
>> efficient even after that, then we probably need to think about =
>> inserting such efficient handling into code we generate, in a way you =
>> inserted ChecLoadTraceRef..something :).
>> 
>> --
>> Dragi=C5=A1a Duri=C4=87
>> dragisha at m3w.org
>> 
>> 
>> 
>> On Apr 30, 2013, at 9:21 AM, Tony Hosking wrote:
>> 
>>> I used to use pthread specifics but I think jay changed it to C. Not =
>> sure why unless compiler can generate more efficiently via sp hacks. =20
>>> =20
>>> Sent from my iPhone
>>> =20
>>> On 30/04/2013, at 3:42 PM, Dragi=C5=A1a Duri=C4=87 <dragisha at m3w.org> =
>> wrote:
>>> =20
>>>> Is there a specific reason why TLS is done through C, and not through =
>> pthread.(set|get)specific?
>>>> =20
>>>> dd
>>>> =20
>>>> --
>>>> Dragi=C5=A1a Duri=C4=87
>>>> dragisha at m3w.org
>>>> =20
>>>> =20
>>>> =20
>> 
>> 
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>> <html><head></head><body style=3D"word-wrap: break-word; =
>> -webkit-nbsp-mode: space; -webkit-line-break: after-white-space; ">It =
>> probably does=E2=80=A6 Because our interface to pthread specifics is =
>> surely not inlined, and sp hacks most probably are. Still, to access =
>> this C code, a procedure call is inserted=E2=80=A6 If sp hack is more =
>> efficient even after that, then we probably need to think about =
>> inserting such efficient handling into code we generate, in a way you =
>> inserted ChecLoadTraceRef..something :).<div><br><div =
>> apple-content-edited=3D"true">
>> <span class=3D"Apple-style-span" style=3D"border-collapse: separate; =
>> color: rgb(0, 0, 0); font-family: Candara; font-style: normal; =
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>> class=3D"Apple-style-span" style=3D"border-collapse: separate; color: =
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>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; "><span class=3D"Apple-style-span" =
>> style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
>> Helvetica; font-style: normal; font-variant: normal; font-weight: =
>> normal; letter-spacing: normal; line-height: normal; orphans: 2; =
>> text-align: -webkit-auto; text-indent: 0px; text-transform: none; =
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>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; =
>> "><div>--</div></div></span></div></span><span class=3D"Apple-style-span" =
>> style=3D"font-family: Helvetica; ">Dragi=C5=A1a Duri=C4=87</span><span =
>> class=3D"Apple-style-span" style=3D"border-collapse: separate; color: =
>> rgb(0, 0, 0); font-family: Helvetica; font-style: normal; font-variant: =
>> normal; font-weight: normal; letter-spacing: normal; line-height: =
>> normal; orphans: 2; text-align: -webkit-auto; text-indent: 0px; =
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>> 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; "><span class=3D"Apple-style-span" =
>> style=3D"border-collapse: separate; color: rgb(0, 0, 0); font-family: =
>> Helvetica; font-style: normal; font-variant: normal; font-weight: =
>> normal; letter-spacing: normal; line-height: normal; orphans: 2; =
>> text-align: -webkit-auto; text-indent: 0px; text-transform: none; =
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>> 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; "><div><a =
>> href=3D"mailto:dragisha at m3w.org">dragisha at m3w.org</a></div><div><br></div>=
>> </div></span></div></span></span><br class=3D"Apple-interchange-newline">
>> </div>
>> <br><div><div>On Apr 30, 2013, at 9:21 AM, Tony Hosking wrote:</div><br =
>> class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><meta =
>> http-equiv=3D"content-type" content=3D"text/html; charset=3Dutf-8"><div =
>> dir=3D"auto"><div>I used to use pthread specifics but I think jay =
>> changed it to C. Not sure why unless compiler can generate more =
>> efficiently via sp hacks.  <br><br>Sent from my =
>> iPhone</div><div><br>On 30/04/2013, at 3:42 PM, Dragi=C5=A1a Duri=C4=87 =
>> <<a href=3D"mailto:dragisha at m3w.org">dragisha at m3w.org</a>> =
>> wrote:<br><br></div><blockquote type=3D"cite"><div>Is there a specific =
>> reason why TLS is done through C, and not through =
>> pthread.(set|get)specific?<div><br></div><div>dd</div><div><br><div =
>> apple-content-edited=3D"true">
>> <span class=3D"Apple-style-span" style=3D"border-collapse: separate; =
>> font-family: Candara; font-style: normal; font-variant: normal; =
>> font-weight: normal; letter-spacing: normal; line-height: normal; =
>> orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
>> none; white-space: normal; widows: 2; word-spacing: 0px; =
>> -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: =
>> 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><span =
>> class=3D"Apple-style-span" style=3D"border-collapse: separate; =
>> font-family: Helvetica; font-style: normal; font-variant: normal; =
>> font-weight: normal; letter-spacing: normal; line-height: normal; =
>> orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
>> none; white-space: normal; widows: 2; word-spacing: 0px; =
>> -webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: =
>> 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; "><span class=3D"Apple-style-span" =
>> style=3D"border-collapse: separate; font-family: Helvetica; font-style: =
>> normal; font-variant: normal; font-weight: normal; letter-spacing: =
>> normal; line-height: normal; orphans: 2; text-align: -webkit-auto; =
>> text-indent: 0px; text-transform: none; white-space: normal; widows: 2; =
>> word-spacing: 0px; -webkit-border-horizontal-spacing: 0px; =
>> -webkit-border-vertical-spacing: 0px; =
>> -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; =
>> "><div>--</div></div></span></div></span><span class=3D"Apple-style-span" =
>> style=3D"font-family: Helvetica; ">Dragi=C5=A1a Duri=C4=87</span><span =
>> class=3D"Apple-style-span" style=3D"border-collapse: separate; =
>> font-family: Helvetica; font-style: normal; font-variant: normal; =
>> font-weight: normal; letter-spacing: normal; line-height: normal; =
>> orphans: 2; text-align: -webkit-auto; text-indent: 0px; text-transform: =
>> none; white-space: normal; widows: 2; word-spacing: 0px; =
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>> 0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; "><span class=3D"Apple-style-span" =
>> style=3D"border-collapse: separate; font-family: Helvetica; font-style: =
>> normal; font-variant: normal; font-weight: normal; letter-spacing: =
>> normal; line-height: normal; orphans: 2; text-align: -webkit-auto; =
>> text-indent: 0px; text-transform: none; white-space: normal; widows: 2; =
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>> -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>> auto; -webkit-text-stroke-width: 0px; font-size: medium; "><div =
>> style=3D"word-wrap: break-word; -webkit-nbsp-mode: space; =
>> -webkit-line-break: after-white-space; "><div><a =
>> href=3D"mailto:dragisha at m3w.org">dragisha at m3w.org</a></div><div><br></div>=
>> </div></span></div></span></span><br class=3D"Apple-interchange-newline">
>> </div>
>> =
>> <br></div></div></blockquote></div></blockquote></div><br></div></body></h=
>> tml>=
>> 
>> --Apple-Mail=_EEF8E283-B126-4B87-BA54-81432C085954--