ingo molnar

A recent discussion on the Linux Kernel mailing list noted that threaded 64-bit applications suffer a drastic slowdown in pthread_create performance when stack utilization goes above 4GB.

Ingo Molnar offered an explanation of the problem, "unfortunately MAP_32BIT use in 64-bit apps for stacks was apparently created without foresight about what would happen in the MM when thread stacks exhaust 4GB.

Embedded Linux developer services provider Timesys is distributing a real-time Linux kernel for ARM9-based Atmel processors.

The 2.6.24.4-rt4 kernel includes Ingo Molnar and Thomas Gleixner's RT_PREEMPT patch, along with patches for high-resolution timers and other board-specific features for Atmel reference

Corrado writes "There is a big discussion going on over removing a bit of non-preemptable code from the Linux kernel.

'As some of the latency junkies on lkml already know, commit 8e3e076 in v2.6.26-rc2 removed the preemptable BKL feature and made the Big Kernel Lock a spinlock and thus turned it into non-preemptable code again.

"This commit returned the BKL code to the 2.6.7 state of affairs in essence," began Ingo Molnar.

"As some of the latency junkies on lkml already know, commit 8e3e076 in v2.6.26-rc2 removed the preemptible BKL feature and made the Big Kernel Lock a spinlock and thus turned it into non-preemptible code again.

This commit returned the BKL code to the 2.6.7 state of affairs in essence," began Ingo Molnar.

He noted that this had a very negative affect on the real time kernel efforts, adding that Linux creator Linus Torvalds indicated the only acceptable way forward was to completely remove the BKL.

Andrew Morton replied to a commit message making 4k stacks the default, saying, "this patch will cause kernels to crash." Ingo Molnar replied, "what mainline kernels crash and how will they crash?

"Finally found it ... the patch below solves the sparsemem crash and the test system boots up fine now," announced Ingo Molnar.

He described the patch as fixing a "memory corruption and crash on 32-bit x86 systems.