digitalmars.D - Removing the Lock for Small GC Allocations: Clarification of GC
- dsimcha (14/14) Dec 31 2011 I have a plan to avoid the GC lock for most small (<1 page) GC
- =?UTF-8?B?QWxleCBSw7hubmUgUGV0ZXJzZW4=?= (4/17) Jan 01 2012 AFAIK dynamic libraries don't have the same GC instance running as an
- Martin Nowak (4/17) Jan 01 2012 Not for shared libraries.
I have a plan to avoid the GC lock for most small (<1 page) GC allocations. I hope to have a pull request within a week or two, in time for the next release. There's one detail I need clarified by Sean, Walter or someone who designed the D GC. Currently small allocations are handled by popping a block off a free list, if a block is available. I plan to make each page owned by a single thread, and make the free lists thread-local. The array of free lists (one for each power of two size) is stored in the Gcx struct. The easiest way to make this array thread-local is to move it out of the Gcx struct and make it global. Is there any reason why >1 instance of Gcx would exist (maybe as an implementation detail of shared libraries, etc.)? If not, what's to point of having the Gcx struct instead of just making its variables global?
Dec 31 2011
On 31-12-2011 23:28, dsimcha wrote:I have a plan to avoid the GC lock for most small (<1 page) GC allocations. I hope to have a pull request within a week or two, in time for the next release. There's one detail I need clarified by Sean, Walter or someone who designed the D GC. Currently small allocations are handled by popping a block off a free list, if a block is available. I plan to make each page owned by a single thread, and make the free lists thread-local. The array of free lists (one for each power of two size) is stored in the Gcx struct. The easiest way to make this array thread-local is to move it out of the Gcx struct and make it global. Is there any reason why >1 instance of Gcx would exist (maybe as an implementation detail of shared libraries, etc.)? If not, what's to point of having the Gcx struct instead of just making its variables global?AFAIK dynamic libraries don't have the same GC instance running as an executable that links to it. Don't quote me on this, though. - Alex
Jan 01 2012
On Sat, 31 Dec 2011 23:28:09 +0100, dsimcha <dsimcha yahoo.com> wrote:I have a plan to avoid the GC lock for most small (<1 page) GC allocations. I hope to have a pull request within a week or two, in time for the next release. There's one detail I need clarified by Sean, Walter or someone who designed the D GC. Currently small allocations are handled by popping a block off a free list, if a block is available. I plan to make each page owned by a single thread, and make the free lists thread-local. The array of free lists (one for each power of two size) is stored in the Gcx struct. The easiest way to make this array thread-local is to move it out of the Gcx struct and make it global. Is there any reason why >1 instance of Gcx would exist (maybe as an implementation detail of shared libraries, etc.)? If not, what's to point of having the Gcx struct instead of just making its variables global?Not for shared libraries. You should probably wrap multiple TLS variables in a struct and put only a reference into TLS to reduce the expense of thread local access.
Jan 01 2012