By adding a 'write_ready' interface following the lines of the existing
'read_ready', VFS plugins become able to propagate the (de-)saturation
of I/O buffers to the VFS user. This information is important when using
a non-blocking file descriptor for writing into a TCP socket. Once the
application observes EAGAIN, it expects a subsequent 'select' call to
return as soon as new I/O buffer space becomes available.
Before this patch, the select call would always return under this
condition, causing an unnecessarily busy write loop.
Issue #4697
The new interface is meant to replace the 'Vfs::Io_response_handler'.
In contrast to the 'Io_response_handler', which had to be called
on a 'Vfs_handle', the new interface does not require any specific
'Vfs_handle'. It is merely meant to prompt the VFS user (like the libc)
to re-attempt stalled I/O operations but it does not provide any
immediate hint, about which of the handles have become ready for
reading/writing.
Issue #4697
This patch removes the 'Insufficient_buffer' exception by returning the
WRITE_ERR_WOULD_BLOCK result value instead. It also eliminates the
superfluous WRITE_ERR_AGAIN and WRITE_ERR_INTERRUPT codes.
Issue #4697
This patch fosters the batching of network packets transferred by the
lwIP stack over the NIC connection. It replaces the eager submission of
the packet-stream's data-flow signals by explicit wakeup notifications.
The commit also increases the NIC session's buffer size from 128 to 1024
packets.
Issue #4697
...and tighten constness in adjacent code parts.
The VFS-internal synchronization via mutexes is no longer needed because
the access to the VFS is serialized by the VFS client, i.e., the libc.
Issue #4697
This patch facilitates the batching of I/O operations in the VFS library
by replacing the implicit wakeup of remote peer (via the traditional
packet-stream interface like 'submit_packet') by explicit wakeup
signalling.
The wakeup signalling is triggered not before the VFS user settles down.
E.g., for libc-based applications, this is the case if the libc goes
idle, waiting for external I/O.
In the case of a busy writer to a non-blocking file descriptor or socket
(e.g., lighttpd), the remote peers are woken up once a write operation
yields an out-count of 0.
The deferring of wakeup signals is accommodated by the new 'Remote_io'
mechanism (vfs/remote_io.h) that is designated to be used by all VFS
plugins that interact with asynchronous Genode services for I/O.
Issue #4697
The change of the queue size from 16 to 32 has negligible costs (4 KiB
instead of 2 KiB for the packet-stream queues) while facilitating the
batching of many small consecutive write operations.
Issue #4697
This is required for scenarios in which a device appears at a later
point in time. If the ROM is not updated, the device_by_type() method may
operate on an outdated dataspace and never find the device it is waiting for.
To prevent caching side-effects of USB DMA memory taken from the packet stream
all allocations of USB packets need to be on separated cachelines at least.
Fixgenodelabs/genode#4655
This patch equips the pin-driver framework with support for the
time-multiplexed operation of a pin as output or input. This is needed
when implementing I2C communication via a bit-banging driver.
To operate pin in both directions, a driver obtains both a pin-state and
a pin-control session for the same pin. The pin-state session can be
used to sense the current pin state. The control session allows the
client to set the pin to high or low (using the 'state' method), or to
set it to high-impedance via the 'yield' method. Once switched to
high-impedance, the pin can be used as input.
Issue genodelabs/genode-allwinner#10
On-demand initialization prevents read-write operations on BARs of
invalid devices at construction time, which may result in surprising
behavior later on, for example, when resetting X260 notebooks via ACPI
information.
Instead of allowing the client to set a caching attribute
in the io_mem() call of the device interface, which was
only used to decide in between of the memory being
write-combined or not, remove it from the API.
Instead use the information delivered by the devices ROM,
whether memory from a PCI BAR is prefetchable or not,
to decide whether it is mapped write-combined or not.
Ref genodelabs/genode#4578
Memory descriptors in PCI BARs have a prefetchable bit, which can
be used to optimize memory access when setting, e.g. write-combined
in page-table entries.
Ref genodelabs/genode#4578
In case of the GPU multiplexer, we need to delegate MMIO memory
to the framebuffer client in form of a managed dataspace. To be
able to attach a given Platform::Device::Mmio object to a region map
we need to access its capability.
Ref genodelabs/genode#4578
In case a driver is waiting for data, is should only investigate 'pos'.
It should not advance the ring in any way until there is data available.
issue #4609
This patch splits the querying of the number of directory entries from
the directory's 'status' information. Subsuming the number of directory
entries as part of the status makes 'stat' calls too costly for some
file systems that need to read a directory for determining the number of
entries. So when stat'ing the entries of one directory that contains sub
directories, all entries of each sub directory are visited.
Thanks to Cedric Degea for pointing out this performance bottleneck!
With this change, the 'status' function returns a 'Status::size' value
of 0 when called for a directory handle.
Fixes#4603
The `with_sub_node` method is renamed to `with_optional_sub_node` to
better reflect that the non-existence of a sub node with the desired type is
ignored.
At the same time, the new `with_sub_node` now takes a second functor that is
called when no sub node of the desired type exists.
genodelabs/genode#4600
By using the new functions provided by the base API, this patch removes
the dependency of several components from include/decorator/xml_utils.h.
Issue #4584
The NIC router used to send an ICMP "Destination Unreachable" packet as
response to every unroutable IPv4 packet. However, RFC 1812 section 4.3.2.7
defines certain properties that must be fullfilled by an incoming packet in
order to be answered with this type of ICMP. One requirement is that the packet
is no IPv4 multicast.
This commit prevents sending the mentioned ICMP response for unroutable IPv4
multicasts and instead drops them silently.
Fixes#4563
The pci_decode has to extract the additional fields from the PCI configuration
space. The platform driver again has to parse and forward the knowledge too.
The PCI BAR indices are exported when info="yes" is set in the policy node for
the corresponding session.
Fixgenodelabs/genode#4577
The base address of I/O ports has a different encoding than
those of I/O memory. This needs to be encountered in the PCI
config helper utilities.
Fixgenodelabs/genode#4576
In overload situations, i.e. when a sender fills up the entire buffer, we land
in situations where the sender receives an ack_avail signal, releases one
packet, allocates and sends a packet and fails to allocate a second packet.
This is especially relevant if the receiver does not batch ack_avail signals
(such as vfs_lwip). In those ping-pong scheduling scenarios, the overhead from
catching the Packet_alloc_failed exception becomes significant. In case of the
NIC router, we will land in an overload situation if the sender is faster than
the receiver. The packet buffer will be filled up at some point and the NIC
router starts to drop packets. For every dropped packet, we currently have to
catch the Packet_alloc_failed exception.
This commit adds a new method alloc_packet_attempt to Packet_stream_source that
has almost the same signature as the older alloc_packet method but returns
an Attempt<Packet_descriptor, Alloc_packet_error> object. As the method already
used the allocator back end exception-less, changes on lower levels were not
needed. Furthermore, the NIC router was modified to use the new exception-less
alloc_packet_attempt instead of alloc_packet.
Ref #4555
The checksums for forwarded/routed UDP, TCP and ICMP, used to be always
re-calculated from scratch in the NIC router although the router changes only
a few packet fields. This commit replaces the old approach whereever sensible
with an algorithm for incremental checksum updates suggested in RFC 1071.
The goal is to improve router performance.
Ref #4555
The checksums for forwarded/routed IPv4, used to be always re-calculated from
scratch in the NIC router although the router changes only a few packet fields.
This commit replaces the old approach whereever sensible with an algorithm for
incremental checksum updates suggested in RFC 1071. The goal is to improve
router performance.
Ref #4555
Prevent public reflection of the only internally used 'init_sum' argument in
'uint16_t internet_checksum(...)' that, in addition, added a default value to
the function interface.
Ref #4555
The wakeup call only emits a single signal as it assumed both are
handled by the same signal handler. However, the original implementation
did not reset the wakeup_needed variable properly.
genodelabs/genode#4555
When using signal batching, ack_avail and packet_avail should always
be emitted and preferred over ready_to_submit and ready_to_ack.
A signal receiver might decide to not register the ready_to_* signals when it
handles congestion by dropping packets. The Nic router is an example of
such a signal receiver.
genodelabs/genode#4555
