diff options
| -rw-r--r-- | advantages.mdwn | 2 | ||||
| -rw-r--r-- | glibc/fork.mdwn | 51 | ||||
| -rw-r--r-- | open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow.mdwn | 5 | ||||
| -rw-r--r-- | open_issues/performance/fork.mdwn | 8 | ||||
| -rw-r--r-- | open_issues/virtualization.mdwn | 7 | ||||
| -rw-r--r-- | rpc.mdwn | 14 |
6 files changed, 77 insertions, 10 deletions
diff --git a/advantages.mdwn b/advantages.mdwn index 18e6506b..8b41f3cd 100644 --- a/advantages.mdwn +++ b/advantages.mdwn @@ -51,6 +51,8 @@ it runs efficiently on both single processors and symmetric multiprocessors. The Hurd interfaces are designed to allow transparent network clusters (*collectives*), although this feature has not yet been implemented. +See also [[unsorted/hurd-migr]] ([[!taglink open_issue_documentation]]). + --> The Hurd is an attractive platform for learning how to become a kernel hacker diff --git a/glibc/fork.mdwn b/glibc/fork.mdwn new file mode 100644 index 00000000..564d9d5b --- /dev/null +++ b/glibc/fork.mdwn @@ -0,0 +1,51 @@ +[[!meta copyright="Copyright © 2010 Free Software Foundation, Inc."]] + +[[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable +id="license" text="Permission is granted to copy, distribute and/or modify this +document under the terms of the GNU Free Documentation License, Version 1.2 or +any later version published by the Free Software Foundation; with no Invariant +Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] + +On [[Unix]] systems, `fork` is a rather simple system call. + +Our implementation in [[glibc]] is and needs to be rather bulky. + +For example, it has to duplicate all port rights for the new [[Mach +task|microkernel/mach/task]]. The address space can simply be duplicated by +standard means of the [[microkernel/Mach]], but as [[file descriptor]]s (for +example) are a concept that is implemented inside [[glibc]] (based on [[Mach +port|microkernel/mach/port]]s), these have to be duplicated from userspace, +which requires a small number of [[RPC]] for each of them. + +In sum, [[this affects performance|open_issues/performance/fork]] when new +processes are continuously being spawned from the shell, for example. + +Often, a `fork` call will eventually be followed by an `exec`, which will in +turn close (most of) the duplicated port rights. Unfortunately, this cannot be +known at the time the `fork` executing, so the code calling `fork` has to be +modified, and the `fork`, `exec` combo be replaced by a `posix_spawn` call, for +example, to avoid this work of duplicating each port right, then closing each +again. + +As far as we know, Cygwin has the same problem of `fork` being a nontrivial +operation. Perhaps we can learn from what they're been doing? Also, perhaps +they have patches for software packages, to avoid using `fork` followed by +`exec`, for example. + + +# TODO + + * [[fork: mach_port_mod_refs: + EKERN_UREFS_OWERFLOW|open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow]] + ([[!taglink open_issue_glibc]]). + + * Include de-duplicate information from elsewhere: [[hurd-paper]], + [[hurd-talk]] [[hurd/ng/trivialconfinementvsconstructorvsfork]], + [[open_issues/resource_management_problems/zalloc_panics]] ([[!taglink + open_issue_glibc open_issue_documentation]]). + + * We no longer support `MACH_IPC_COMPAT`, thus we can get rid of the `err = + __mach_port_allocate_name ([...]); if (err == KERN_NAME_EXISTS)` code + ([[!taglink open_issue_glibc]]). diff --git a/open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow.mdwn b/open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow.mdwn index b6ecb92a..e80a5661 100644 --- a/open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow.mdwn +++ b/open_issues/fork_mach_port_mod_refs_ekern_urefs_owerflow.mdwn @@ -159,3 +159,8 @@ The error is 19, `EKERN_UREFS_OVERFLOW`. successfully.) [[!tag open_issue_glibc]] + + +# Discussion + +<http://lists.gnu.org/archive/html/bug-hurd/2010-11/msg00028.html> diff --git a/open_issues/performance/fork.mdwn b/open_issues/performance/fork.mdwn index 390f6b99..2748be53 100644 --- a/open_issues/performance/fork.mdwn +++ b/open_issues/performance/fork.mdwn @@ -10,13 +10,7 @@ License|/fdl]]."]]"""]] [[!tag open_issue_glibc open_issue_hurd]] -On Unix systems, `fork` is a rather simple system call. Our implementation in -[[glibc]] is / needs to be rather bulky. TODO: elaborate. - -This affects performance when new processes are continuously being spawned from -the shell, for example. - -Alternatives: use `posix_spawn`. Others? +Our [[`fork` implementation|glibc/fork]] is nontrivial. To do: hard numbers. [[Microbenchmarks]]? diff --git a/open_issues/virtualization.mdwn b/open_issues/virtualization.mdwn index ebf86a2d..343f624a 100644 --- a/open_issues/virtualization.mdwn +++ b/open_issues/virtualization.mdwn @@ -20,6 +20,13 @@ An index of things to work on w.r.t. virtualization. * [[hurd/subhurd]] / [[hurd/neighborhurd]] +<!-- + + * There's talking about *collectives* in the Hurd RM, on [[/advantages]] and + [[unsorted/hurd-migr]] ([[!taglink open_issue_documentation]]). + +--> + * [[Implementing_Hurd_On_Top_of_Another_System]] * Unix / Linux @@ -1,11 +1,19 @@ -[[!meta copyright="Copyright © 2007, 2008 Free Software Foundation, Inc."]] +[[!meta copyright="Copyright © 2007, 2008, 2010 Free Software Foundation, +Inc."]] [[!meta license="""[[!toggle id="license" text="GFDL 1.2+"]][[!toggleable id="license" text="Permission is granted to copy, distribute and/or modify this document under the terms of the GNU Free Documentation License, Version 1.2 or any later version published by the Free Software Foundation; with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts. A copy of the license -is included in the section entitled -[[GNU Free Documentation License|/fdl]]."]]"""]] +is included in the section entitled [[GNU Free Documentation +License|/fdl]]."]]"""]] RPC stands for remote procedure call. + + +# See Also + + * [[Mach RPC|microkernel/mach/rpc]]s + + * the [[Hurd's rpctrace|hurd/debugging/rpctrace]] |